HVAC Code Lookup

Rheem and Ruud fault codes

40 documented codes for Rheem and Ruud furnaces, each cited to the manufacturer's own manual. Find your code in the table, then jump to what it means, the likely causes, what you can safely check, and when to call a technician.

Ruud is the same manufacturer (Rheem Manufacturing Company) and uses the identical integrated furnace control and the identical fault-code set: the Ruud U97V, U96V and U801 furnaces are the same units as the Rheem R97V, R96V and R801. Rheem publishes one installation manual per platform with a "(-)" brand placeholder on the cover (e.g. "(-)97V SERIES") covering both the R and U model prefixes. Older Rheem 90+ furnaces (RGRA/RGRB/RGTA/RGRS/RGTS/RGRT) use a UT Electronic Controls 1028-928 board with green-LED blink codes instead of the 7-segment display. That is why Ruud codes are on this page: they mean the same thing on either brand.

Furnace codes

CodeMeaningSeverity
0StandbyStatus
HGas heat modeStatus
CCooling modeStatus
FContinuous fan modeStatus
dFDefrost mode on a dual-fuelStatus
d1No model dataHard lockout
d4No valid model data on the model data cardWarning
d6Horsepower conflict on the model data cardWarning
10One-hour lockoutSoft lockout
11Failed ignitionSoft lockout
12Low flame senseWarning
13Flame lost after it was establishedWarning
14Flame present with the gas valve offSafety fault
20Twinning faultWarning
22Main limit openSoft lockout
23HALCSoft lockout
26Line and neutral reversed, or poor groundHard lockout
30Open fuseHard lockout
33Over-temperature switchSafety fault
44Low pressure switch closed with the inducer offSafety fault
45Low pressure switch open with the inducer running on high speedSoft lockout
46Low pressure switch open with the inducer running on low speedSoft lockout
55High pressure switch closed with the inducer offSafety fault
57High pressure switch open with the inducer on high speedSoft lockout
58Water circuit openSoft lockout
59Water sensed in the collector boxSoft lockout
60Blower fault, blower can still runWarning
61Blower fault, motor cannot runHard lockout
66Blower cutbackWarning
68No blower communicationsHard lockout
65Mid pressure switch closed when it should be openWarning
67Mid pressure switch open when it should be closedWarning
71Inducer faultSoft lockout
77No gas valve feedback signalHard lockout
93Internal control fault detectedHard lockout
11 blink of the green status LED, repeatingSoft lockoutSoft lockout
22 blinks of the green status LED, repeatingPressure switch circuit open - the switch failed to closeSoft lockout
33 blinks of the green status LED, repeatingLimit circuit openSoft lockout
44 blinks of the green status LED, repeatingPressure switch circuit closed when it should be open - the switch is proving closed before the inducer startsSafety fault
55 blinks of the green status LED, repeatingTwin faultWarning

Rheem furnace code 0: Standby

Status

Standby. The furnace is idle: there is no fault present and no call from the thermostat. This is the normal display when nothing is running.

Manual wording: “STANDBY MODE ... This code is displayed anytime there is no fault present and no thermostat call present. The furnace is idle.”

Documented for: (-)97V, (-)96V, (-)801S/(-)801P and other 7-segment Rheem/Ruud furnace controls

Likely causes, most common first

  1. Normal standby - no thermostat demand

What you can safely check yourself

  • Nothing to do. If you expected heat, check the thermostat is set to HEAT and the setpoint is above room temperature.

When to call a technician

If the thermostat is calling for heat and the display still reads 0, the thermostat wiring or the control may need a technician.

Sources

Rheem furnace code H: Gas heat mode

Status

Gas heat mode. The furnace is running a heat call. Lower-case "h" means the thermostat is asking for low-stage heat, upper-case "H" means high-stage heat.

Manual wording: “GAS HEAT MODE ... The lower-case "h" is displayed when the thermostat is requesting low gas heat and the upper-case "H" is displayed when the thermostat is requesting high-stage gas heat.”

Documented for: (-)97V, (-)96V, (-)801S/(-)801P

Likely causes, most common first

  1. Normal heating operation

What you can safely check yourself

  • Nothing to do - this is normal operation.

When to call a technician

No action needed unless the furnace is running but not producing heat.

Sources

Rheem furnace code C: Cooling mode

Status

Cooling mode. The furnace blower is responding to a cooling (or heat-pump) call from the thermostat. Lower-case "c" is low-stage cooling, upper-case "C" is high-stage cooling.

Manual wording: “COOLING MODE ... This code is displayed anytime there is a call for cooling.”

Documented for: (-)97V, (-)96V; on (-)801S/(-)801P the same C means COMPRESSOR ON (cooling or heat-pump heat)

Likely causes, most common first

  1. Normal cooling operation

What you can safely check yourself

  • Nothing to do - this is normal operation.

When to call a technician

No action needed unless the air conditioner is not actually cooling.

Sources

Rheem furnace code F: Continuous fan mode

Status

Continuous fan mode. The thermostat is asking for the blower to run continuously with no heating or cooling.

Manual wording: “CONTINUOUS FAN MODE ... This code is displayed anytime there is a call for continuous fan from the thermostat.”

Documented for: (-)97V, (-)96V, (-)801S/(-)801P

Likely causes, most common first

  1. Thermostat fan switch set to ON

What you can safely check yourself

  • If you did not want the fan running all the time, set the thermostat fan switch from ON to AUTO.

When to call a technician

No action needed - this is a normal operating code.

Sources

Rheem furnace code DF: Defrost mode on a dual-fuel

Status

Defrost mode on a dual-fuel (heat pump plus gas furnace) system. The heat pump is running a defrost cycle and the furnace is firing at fixed low-stage heat to temper the air.

Manual wording: “DEFROST MODE ... This code indicates that the heat-pump is in defrost mode (dual-fuel systems only) and furance is operating for defrost operation which is fixed at low-stage gas heating operation.”

Documented for: (-)97V, (-)96V dual-fuel installations

Likely causes, most common first

  1. Normal heat-pump defrost cycle on a dual-fuel system

What you can safely check yourself

  • Nothing to do. Steam coming off the outdoor unit during defrost is normal.

When to call a technician

If the outdoor unit stays iced over after defrost cycles, a technician should check the heat pump.

Sources

Rheem furnace code D1: No model data

Hard lockout

No model data. The control cannot find the electronically stored model data that tells it how to run the blower, so the furnace will not operate in any mode. Usually the model data card is missing from the control board.

Manual wording: “NO MODEL DATA ... This code is displayed anytime there is no model data at the furnace. ... No operation (including thermostat) will be permitted without the model data.”

Documented for: (-)97V, (-)96V communicating furnaces

Likely causes, most common first

  1. Model data card missing from connector P6 on the furnace control
  2. The original model data card was lost or disconnected when the furnace control was replaced

When to call a technician

This is a control-board / model-data-card problem. A technician must install the correct model data card for your furnace - the card is furnace-specific and using one from another unit can damage the heat exchanger.

Sources

Rheem furnace code D4: No valid model data on the model data card

Warning

No valid model data on the model data card. The card plugged into position P6 is blank, missing or corrupted, but a good copy of the model data still lives in the control's memory, so the furnace should keep running normally.

Manual wording: “NO VALID MODEL DATA ON MODEL DATA CARD ... The model data card inserted into the slot at position P6 of the furnace control is corrupt and can not be used OR there is no model data card installed at all.”

Documented for: (-)97V, (-)96V communicating furnaces

Likely causes, most common first

  1. No information on the model data card (blank card)
  2. The card is not present
  3. The model data card has corrupted and cannot be properly read

What you can safely check yourself

  • Nothing homeowner-serviceable. The furnace should still heat and cool normally with this code showing in standby.

When to call a technician

A technician should fit the correct replacement memory card. Never use a card from a different furnace or from a condenser/air handler.

Sources

Rheem furnace code D6: Horsepower conflict on the model data card

Warning

Horsepower conflict on the model data card. The horsepower the blower motor reports does not match the horsepower stored on the model data card, though the data stored in the control itself does match. The furnace should still operate.

Manual wording: “HORSEPOWER CONFLICT ON MODEL DATA CARD ... The horsepower reported by the motor does not match the horsepower stored in memory in the model data of the model data card.”

Documented for: (-)97V, (-)96V communicating furnaces

Likely causes, most common first

  1. The blower motor has recently been replaced and the wrong horsepower motor was used
  2. The model data card or furnace control has recently been replaced and the wrong card or replacement control was used

What you can safely check yourself

  • Nothing homeowner-serviceable. The furnace should still operate normally with this code showing in standby.

When to call a technician

A technician needs to identify the correct motor and/or model data card for your furnace model and serial number and replace the mismatched part.

Sources

Rheem furnace code 10: One-hour lockout

Soft lockout

One-hour lockout. The control has shut gas heating down for one hour after repeated failures. Code 10 alternates on the display with the code for the fault that caused it - most often 11 (failed ignition), 13 (flame lost), 14 (unexpected flame), 59 (water sensed) or 61 (blower not running). Cooling still works.

Manual wording: “ONE-HOUR LOCKOUT ... When a failed ignition has occurred four times in a row, the control enters one-hour lockout and fault codes "10" and "11" will be displayed alternately at the seven-segment display.”

Documented for: (-)97V, (-)96V, (-)801S/(-)801P

Likely causes, most common first

  1. Four failed ignition attempts in a row (shown with code 11)
  2. Flame lost five times in a row (shown with code 13)
  3. Unexpected flame detected (shown with code 14)
  4. Repeated water-sensed condition in the collector box (shown with code 59)
  5. Dead blower declared after the main limit stayed open more than 150 seconds (shown with code 61)

What you can safely check yourself

  • Note the second code that alternates with 10 - that is the real fault.
  • Check and replace a dirty air filter.
  • Make sure supply and return registers are open and unblocked.
  • Check the outdoor intake and exhaust pipe terminations for snow, ice, leaves or nests.

When to call a technician

Code 10 is only the lockout timer. The alternating companion code is the actual failure, and most of those (ignition, flame sensing, blower, condensate) need a technician.

Sources

Rheem furnace code 11: Failed ignition

Soft lockout

Failed ignition. The furnace opened the gas valve but never proved a flame. It retries with a 20-second post-purge between attempts; after the fourth consecutive failure it goes to a one-hour lockout and alternates 11 with 10.

Manual wording: “FAILED IGNITION ... This fault is displayed at the furnace control after the first failed ignition attempt. ... After four failed ignition attempts, the IFC enters one-hour lockout and the dual faults "11" and "10" are alternately displayed.”

Documented for: (-)97V, (-)96V, (-)801S/(-)801P

Likely causes, most common first

  1. The flame sense rod is unable to sense flame - it may need cleaning or may not be properly connected
  2. The gas valve may be turned off
  3. The igniter is not working properly, is not properly connected, or the spark location is not correct
  4. The furnace control may not be working properly and may need to be replaced
  5. The flame may not be properly spreading from the first burner to the last

What you can safely check yourself

  • Check that the furnace doors are fully seated and latched.
  • Check and replace a dirty air filter.
  • Try one power cycle at the furnace switch or breaker to clear the lockout.
  • Check the outdoor intake and exhaust terminations for snow, ice or debris.

When to call a technician

If the code returns, the flame sensor, igniter, gas valve or gas supply needs a technician. Do not open the burner compartment or touch the gas valve, flame sensor or igniter yourself.

Sources

Rheem furnace code 12: Low flame sense

Warning

Low flame sense. The flame current the control reads from the flame sense rod is weak or marginal. The furnace keeps running normally, but if the signal falls further the code escalates to 13 (flame lost) or 11 (failed ignition).

Manual wording: “LOW FLAME SENSE ... The flame sense current from the flame sense rod at the furnace control (or I.F.C.) is weak or marginal at best.”

Documented for: (-)97V, (-)96V, (-)801S/(-)801P

Likely causes, most common first

  1. The flame sense rod needs cleaning, is not properly connected, or its wiring to the control is shorted or open
  2. An improperly mounted or poorly grounded flame sensor

What you can safely check yourself

  • Nothing homeowner-serviceable - the flame sensor is inside the burner compartment. Book service before it turns into a no-heat call.

When to call a technician

Code 12 is an early warning. Have a technician clean or replace the flame sense rod and check the furnace ground before it becomes a lockout.

Sources

Rheem furnace code 13: Flame lost after it was established

Warning

Flame lost after it was established. The burner lit and the control proved flame, then the flame signal disappeared mid-cycle. The control post-purges and retries; five losses in a row send it to a one-hour lockout showing 13 alternating with 10.

Manual wording: “FLAME LOST AFTER ESTABLISHED ... After a successful ignition trial, the flame (which was properly sensed) is no longer sensed.”

Documented for: (-)97V, (-)96V, (-)801S/(-)801P

Likely causes, most common first

  1. The flame sense rod needs cleaning, is not properly connected, or its wiring to the control is shorted or open
  2. An improperly mounted or poorly grounded flame sensor
  3. Flame pattern may be unstable

What you can safely check yourself

  • Check that the burner-compartment door and blower door are fully seated - the manual calls out door and gasket seals as a cause of unstable flame.
  • Check and replace a dirty air filter.

When to call a technician

Flame sensing, burner assembly and heat-exchanger seal checks are all technician work. If code 13 keeps returning, get it diagnosed.

Sources

Rheem furnace code 14: Flame present with the gas valve off

Safety fault

Flame present with the gas valve off. The control is seeing flame when there should be none. The blower and inducer run at maximum until the condition clears, then the furnace enters a one-hour lockout showing 14 alternating with 10. The manual calls this extremely critical.

Manual wording: “FLAME PRESENT WITH GAS VALVE OFF ... This fault indicates flame is present when it should not be. Flame is seen to be present when the gas valve is supposed to be off.”

Documented for: (-)97V, (-)96V, (-)801S/(-)801P

Likely causes, most common first

  1. Field mis-wiring of 24VAC to the gas valve main solenoid
  2. Faulty gas valve stuck in the OPEN position
  3. Faulty furnace control (signal improperly sensed when it should not be sensed at all)

What you can safely check yourself

  • If you smell gas, leave the building and call your gas utility from outside.
  • Otherwise, leave the furnace alone and call for service.

When to call a technician

Call a technician immediately. A gas valve stuck open is a gas-safety fault - do not attempt any troubleshooting, and never bypass or jumper anything on the gas valve circuit.

Sources

Rheem furnace code 20: Twinning fault

Warning

Twinning fault. Two furnaces installed side by side and wired to run together (twinned) are not communicating or are not set up correctly.

Manual wording: “20 TWINNING FAULT”

Documented for: (-)801S/(-)801P and other single-stage controls with the twinning feature

Likely causes, most common first

  1. Twinning wiring or dipswitch setup between the two furnace controls is incorrect
  2. The two control boards are not the same part number, or their transformers are not in phase

When to call a technician

Twinned installations are commissioned by a technician - the twin wiring, dipswitch settings and transformer phasing all have to be checked with the power on.

Source

Rheem furnace code 22: Main limit open

Soft lockout

Main limit open. The temperature inside the heat exchanger area has climbed above a safe preset value, so the limit switch opened and gas heating is blocked until it cools. Almost always an airflow problem. If the limit stays open more than 150 seconds the control also shows 61 and can go to hard lockout.

Manual wording: “MAIN LIMIT OPEN ... The main limit has opened or is sensed to be opened. This normally means that the temperture inside the heat exchanger area has gone above a certain predetermined critical value and heating operation is not permitted until the limit cools to within normal parameters.”

Documented for: (-)97V, (-)96V; on (-)801S/(-)801P code 22 reads MAIN LIMIT OR HALC OPEN

Likely causes, most common first

  1. No airflow
  2. Insufficient airflow
  3. Faulty limit control
  4. Loose or faulty wiring
  5. Dead (non-functional) blower
  6. Input too high

What you can safely check yourself

  • Check the air filter and replace it if it is dirty - this is the number one cause.
  • Open all supply registers and clear anything blocking return air grilles.
  • Make sure the blower door is fully closed and seated.
  • Let the furnace cool, then power cycle once at the furnace switch.

When to call a technician

If the code comes back after a clean filter and open registers, the blower, ductwork static pressure, limit control or gas input needs a technician. Never jumper or bypass the limit switch.

Sources

Rheem furnace code 23: HALC

Soft lockout

HALC (heat assist limit control) circuit open. The control does not sense continuity between pins 3 and 5 of connector P1. On furnaces built without an HALC there is a jumper wire in its place, so this code usually means that jumper is not making connection.

Manual wording: “HALC OPEN ... This fault is displayed when the IFC does not sense continuity between pins 3 and 5 of connector P1 on the furnace control.”

Documented for: (-)97V, (-)96V; also listed on the Rheem/Ruud IFC fault-code label as 23 Heat Assist Limit (HALC) Open

Likely causes, most common first

  1. No continuity between pins 3 and 5 of connector P1 on the furnace control

When to call a technician

This is a wiring/jumper repair inside the control compartment - technician work.

Sources

Rheem furnace code 26: Line and neutral reversed, or poor ground

Hard lockout

Line and neutral reversed, or poor ground. The 120V hot and neutral wires feeding the furnace control are swapped, or the control cannot sense a good ground. No heating or cooling will run until it is corrected.

Manual wording: “LINE AND NEUTRAL REVERSED OR POOR GROUND ... This fault code is an indication that line voltage and neutral are reversed to the furnace control or may also be an indication of a grounding issue.”

Documented for: (-)97V, (-)96V, (-)801S/(-)801P

Likely causes, most common first

  1. Line and neutral to the furnace have been interchanged at the furnace
  2. Line voltage and neutral have been interchanged at the disconnect or at the breaker box
  3. Furnace control cannot properly sense ground

When to call a technician

This is line-voltage wiring work. A technician (or an electrician) must meter the supply and correct the polarity and grounding at the furnace, disconnect and panel.

Sources

Rheem furnace code 30: Open fuse

Hard lockout

Open fuse. The low-voltage fuse on the furnace control has blown, normally because of a 24VAC short to common or ground somewhere in the low-voltage wiring. Nothing will run until the short is found and the fuse replaced.

Manual wording: “OPEN FUSE ... The fuse has been opened. This usually occurs when there is a 24VAC short to common or ground on the low-votage side of the transformer.”

Documented for: (-)97V, (-)96V

Likely causes, most common first

  1. An electrical short from low voltage (24VAC) to ground or common has occurred

When to call a technician

A technician must find and repair the short before replacing the fuse - simply swapping the fuse will blow it again and can damage the control.

Sources

Rheem furnace code 33: Over-temperature switch

Safety fault

Over-temperature switch (roll-out) open. A manually reset rollout limit has tripped, which means flames rolled out of the heat exchanger into the burner compartment. The manual describes this as a very serious problem that must be repaired before the furnace runs again.

Manual wording: “OVER-TEMPERATURE SWITCH (ROLL-OUT) OPEN ... This fault will occur when flames have rolled out of the normal area in the heat exchanger and into the burner compartment. This fault should rarely (if ever) be seen in the field and indicates a very serious problem.”

Documented for: (-)97V, (-)96V, (-)801S/(-)801P

Likely causes, most common first

  1. Insufficient venting through either the inlet or exhaust
  2. Loose or faulty wiring
  3. Unstable flame pattern

What you can safely check yourself

  • Turn the furnace off at its switch and leave it off.
  • If you smell gas or see soot, leave the building and call your gas utility from outside.

When to call a technician

Call a technician. Rollout means combustion products left the heat exchanger; the vent system, inducer, gaskets and heat exchanger all have to be inspected. Never push the rollout reset button and put the furnace back in service without a diagnosis.

Sources

Rheem furnace code 44: Low pressure switch closed with the inducer off

Safety fault

Low pressure switch closed with the inducer off. The low pressure switch is proving closed before the inducer even starts, which it should never do. The control tests for this before every heat cycle. The manual warns the switch may be welded closed or deliberately bypassed in the field.

Manual wording: “LOW PRESSURE SWITCH CLOSED, INDUCER OFF ... The low pressure control (or switch) should not be closed when the inducer is not running. If it is, this is a sign of a serious condition. The switch may be welded closed or purposely bypassed in the field.”

Documented for: (-)97V, (-)96V

Likely causes, most common first

  1. Faulty switch
  2. Pressure switch physically bypassed in the field
  3. Loose or faulty wiring
  4. Abnormally high negative pressure present on vent system without inducer running

When to call a technician

Technician only. This is a combustion-safety interlock that is not doing its job - it must be replaced or the field bypass removed, never left in place.

Sources

Rheem furnace code 45: Low pressure switch open with the inducer running on high speed

Soft lockout

Low pressure switch open with the inducer running on high speed. The switch has to close once the inducer starts before ignition is allowed. The inducer keeps trying in five-minute cycles until the switch closes or the heat call ends.

Manual wording: “LOW PRESSURE SWITCH OPEN, INDUCER ON HIGH SPEED ... This fault indicates that the low pressure switch is open when the inducer is energized at high speed.”

Documented for: (-)97V, (-)96V

Likely causes, most common first

  1. Blockage or improper termination in either the inlet or exhaust vents
  2. The flue vent length and/or number of elbows exceeds the maximum number specified
  3. Faulty or disconnected inducer
  4. Faulty control board (inducer relay)
  5. Loose or faulty wiring
  6. Disconnected, blocked, split or cut pressure switch hoses
  7. Wind gusts (sporadic)
  8. Faulty pressure switch

What you can safely check yourself

  • Go outside and check the intake and exhaust pipe terminations for snow, ice, leaves, insect screens or a nest.
  • On a high-efficiency furnace, check the condensate drain and trap for a clog - a full trap can block the vent.
  • Power cycle once at the furnace switch after clearing any blockage.

When to call a technician

If the terminations are clear and the code returns, the inducer, pressure switch, hoses or vent run needs a technician. Never jumper the pressure switch.

Sources

Rheem furnace code 46: Low pressure switch open with the inducer running on low speed

Soft lockout

Low pressure switch open with the inducer running on low speed. Same switch as code 45, but it dropped out after the furnace stepped down to low-fire heat. The furnace post-purges and retries ignition if the heat call is still there.

Manual wording: “LOW PRESSURE SWITCH OPEN, INDUCER ON LOW SPEED ... This fault indicates that the low pressure switch is open when the inducer is energized at low speed.”

Documented for: (-)97V, (-)96V two-stage and modulating furnaces

Likely causes, most common first

  1. Blockage or improper termination in either the inlet or exhaust vents
  2. The flue vent length and/or number of elbows exceeds the maximum number specified
  3. Faulty or disconnected inducer
  4. Faulty control board (inducer relay)
  5. High altitude kit not installed in areas of high elevation
  6. Loose or faulty wiring
  7. Disconnected, blocked, split or cut pressure switch hoses
  8. Wind gusts (sporadic)
  9. Faulty pressure switch

What you can safely check yourself

  • Check the outdoor intake and exhaust terminations for snow, ice or debris.
  • Check the condensate drain and trap for a clog.
  • Power cycle once at the furnace switch after clearing any blockage.

When to call a technician

Vent length, high-altitude kits, inducer and pressure switch work are all technician jobs. Never bypass the pressure switch.

Sources

Rheem furnace code 55: High pressure switch closed with the inducer off

Safety fault

High pressure switch closed with the inducer off. The high pressure switch is proving closed before the inducer starts, which should never happen. As with code 44, the manual warns it may be welded closed or bypassed in the field.

Manual wording: “HIGH PRESSURE SWITCH CLOSED, INDUCER OFF ... The high pressure control (or switch) should not be closed when the inducer is not running. If it is, this is a sign of a serious condition.”

Documented for: (-)97V, (-)96V

Likely causes, most common first

  1. Faulty switch
  2. Pressure switch physically bypassed in the field
  3. Loose or faulty wiring
  4. Abnormally high negative pressure present on vent system without inducer running

When to call a technician

Technician only. A stuck-closed or bypassed pressure switch defeats a combustion-safety interlock and has to be replaced or restored.

Sources

Rheem furnace code 57: High pressure switch open with the inducer on high speed

Soft lockout

High pressure switch open with the inducer on high speed. On a two-stage or modulating furnace the control will usually drop to low fire and keep heating (if the low pressure switch stays closed) rather than shut off completely.

Manual wording: “HIGH PRESSURE SWITCH OPEN, INDUCER ON HIGH SPEED ... This fault indicates that the high pressure switch is open when the inducer is energized at high speed.”

Documented for: (-)97V, (-)96V

Likely causes, most common first

  1. Blockage or improper termination in either the inlet or exhaust vents
  2. The flue vent length and/or number of elbows exceeds the maximum number specified
  3. Faulty or disconnected inducer
  4. Faulty control board (inducer relay)
  5. High altitude kit not installed in areas of high elevation
  6. Loose or faulty wiring
  7. Disconnected, blocked, split or cut pressure switch hoses
  8. Wind gusts (sporadic)
  9. Faulty pressure switch

What you can safely check yourself

  • Check the outdoor intake and exhaust terminations for snow, ice, leaves or a nest.
  • Check the condensate drain and trap for a clog.
  • Power cycle once at the furnace switch after clearing any blockage.

When to call a technician

If the vent terminations are clear and 57 keeps coming back, have a technician check the inducer, pressure switch hoses and total vent length. Never jumper the switch.

Sources

Rheem furnace code 58: Water circuit open

Soft lockout

Water circuit open. The control cannot see continuity between pins 1 and 2 of connector P4, which is how it verifies both collector-box water sensors are present and wired. Gas heat is blocked; cooling still runs.

Manual wording: “WATER CIRCUIT OPEN ... The IFC cannot detect electrical continuity between pins 1 and 2 of connector P4 of the furnace control.”

Documented for: (-)97V, (-)96V condensing furnaces

Likely causes, most common first

  1. Wiring has been damaged between the control or sensor
  2. Connection of P4 at the IFC or at the water sensors is not properly made
  3. Water sensor has been removed

When to call a technician

The water sensors and their wiring are inside the furnace - a technician needs to repair the connection or replace a missing sensor.

Sources

Rheem furnace code 59: Water sensed in the collector box

Soft lockout

Water sensed in the collector box. The control has detected water backing up in the collector box for at least ten seconds and has stopped gas heating. Repeated occurrences send the furnace into a one-hour lockout showing 59 alternating with 10. Cooling still works.

Manual wording: “WATER SENSED ... The IFC looks for current flow from these pins to determine if water is present in the collector box.”

Documented for: (-)97V, (-)96V condensing furnaces

Likely causes, most common first

  1. A blocked condensate drain or the drain trap has become blocked and cannot allow condensate water to flow properly
  2. Wiring to the sensors has been damaged and exposed wiring is touching the furnace sheet metal
  3. Water sensor has been removed from the collector box with wires still attached and the metal probe is touching the sheet metal portion of the furnace

What you can safely check yourself

  • Check the condensate drain line and trap for a clog, and check that the condensate pump (if you have one) is working and its float is not stuck.
  • Make sure the drain line is not kinked, frozen at an outside wall, or draining into a backed-up floor drain.
  • Power cycle once at the furnace switch after clearing the drain.

When to call a technician

If the drain is clear and code 59 returns, the collector box, sensors or their wiring need a technician.

Sources

Rheem furnace code 60: Blower fault, blower can still run

Warning

Blower fault, blower can still run. A non-critical motor fault: the blower keeps running but at less than optimal conditions. Everything, including thermostat calls, continues to work.

Manual wording: “BLOWER FAULT - BLOWER CAN STILL RUN ... A blower fault which is non-critical allows the blower to continue to run but at less-than-optimal conditions.”

Documented for: (-)97V, (-)96V

Likely causes, most common first

  1. The blower has hit the maximum speed or torque limit specified by the manufacturer or is running at the temperature limit because the static pressure is too high

What you can safely check yourself

  • Check and replace a dirty air filter.
  • Open all supply registers and clear anything blocking the return air grilles.

When to call a technician

If a clean filter and open registers do not clear it, the duct system static pressure is too high and a technician needs to measure it and correct the ductwork.

Sources

Rheem furnace code 61: Blower fault, motor cannot run

Hard lockout

Blower fault, motor cannot run. The blower motor has failed or tripped its internal thermal limit and cannot turn. The furnace will not operate in any mode. It is often displayed alternating with 22 (main limit open) or 10 (one-hour lockout).

Manual wording: “BLOWER FAULT - MOTOR CANNOT RUN ... The blower has failed critically or there is a critical motor fault - such as thermal limit trip that prevents the blower motor from running.”

Documented for: (-)97V, (-)96V

Likely causes, most common first

  1. The motor has tripped on thermal limit because of a restriction or bearing failure
  2. The motor Power Factor Correction (P.F.C.) choke is faulty and needs replacing
  3. The furnace model data is faulty or corrupted
  4. Wiring to the motor and/or P.F.C. has become compromised
  5. The blower wheel has become damaged or is not properly attached to the motor shaft
  6. The motor has failed catastrophically

What you can safely check yourself

  • Check and replace a dirty air filter - a restricted filter is a listed cause of the motor overheating.
  • Make sure the blower door is fully closed and seated.
  • Power cycle once at the furnace switch to see if the motor restarts after cooling.

When to call a technician

A blower motor that will not run is a technician job - motor, PFC choke, wiring and blower wheel all have to be checked.

Sources

Rheem furnace code 66: Blower cutback

Warning

Blower cutback. The variable-speed blower is already at its maximum allowed speed or torque but still cannot move the airflow the system needs, because duct static pressure is too high. The manual says this is an operating indicator rather than a true fault, and it is not shown in the first three minutes after a power reset.

Manual wording: “BLOWER CUTBACK ... The blower motor is operating at the highest rpm or torque that specifications allow but the application requires more torque or speed in order to get the desired airflow under the current static pressure conditions.”

Documented for: (-)97V, (-)96V

Likely causes, most common first

  1. The blower has hit the maximum speed or torque limit specified by the manufacturer because the static pressure is too high

What you can safely check yourself

  • Check and replace a dirty air filter.
  • Open every supply register and clear rugs, furniture or boxes off return air grilles.
  • Make sure a high-MERV filter has not been fitted where the duct system cannot handle it.

When to call a technician

If it persists with a clean filter, the ductwork is undersized or restricted. A technician has to measure static pressure and correct the duct system.

Sources

Rheem furnace code 68: No blower communications

Hard lockout

No blower communications. The furnace control cannot talk to the ECM blower motor at all. The furnace will not operate in any mode; if it was heating, the gas valve closes immediately.

Manual wording: “NO BLOWER COMMUNICATIONS ... The furnace control (I.F.C.) can not communicate with the blower motor.”

Documented for: (-)97V, (-)96V

Likely causes, most common first

  1. The wires between the blower motor have been disconnected or there is a poor connection
  2. There is no line voltage to the motor
  3. The furnace model data is faulty or corrupted
  4. The motor has failed catastrophically

What you can safely check yourself

  • Make sure the blower door is fully closed and seated, and that the furnace switch and breaker are on.
  • Power cycle once at the furnace switch.

When to call a technician

Technician job: motor wiring, line voltage to the PFC choke and ECM motor, model data card and the motor itself all have to be checked.

Sources

Rheem furnace code 65: Mid pressure switch closed when it should be open

Warning

Mid pressure switch closed when it should be open. Modulating furnaces use a third (mid) pressure switch to allow the middle firing rates. The furnace still heats, but firing rates between 50% and 65% are forced to 70%.

Manual wording: “MID PRESSURE SWITCH CLOSED, SHOULD BE OPEN ... This fault indicates that the mid pressure switch is electrically closed when it should be open.”

Documented for: (-)97V modulating furnaces only

Likely causes, most common first

  1. Bad wiring to mid pressure switch
  2. Bad mid pressure switch
  3. Bad furnace control

What you can safely check yourself

  • Nothing homeowner-serviceable. The furnace will keep heating, just with slightly less firing-rate range.

When to call a technician

A technician needs to check the mid pressure switch wiring and replace the switch or control as needed.

Source

Rheem furnace code 67: Mid pressure switch open when it should be closed

Warning

Mid pressure switch open when it should be closed. Same modulating-only switch as code 65. The furnace keeps heating but firing rates between 50% and 65% are fixed at 70%.

Manual wording: “MID PRESSURE SWITCH OPEN, SHOULD BE CLOSED ... This fault indicates that the mid pressure switch is electrically open when it should be closed.”

Documented for: (-)97V modulating furnaces only

Likely causes, most common first

  1. Wind gusts
  2. Improper venting
  3. Bad wiring to mid pressure switch
  4. Bad mid pressure switch
  5. Bad furnace control

What you can safely check yourself

  • Check the outdoor intake and exhaust terminations for snow, ice or debris.
  • The manual notes wind gusts can trip it - if it clears when the wind drops, mention that to your technician.

When to call a technician

Vent length and construction, pressure switch and control replacement are technician work.

Source

Rheem furnace code 71: Inducer fault

Soft lockout

Inducer fault. The control is measuring too much or too little current on the inducer (draft motor) circuit. Gas heat is blocked; cooling still runs. The manual notes this can appear harmlessly if power is lost and restored within 30 seconds while the furnace is heating.

Manual wording: “INDUCER FAULT ... This fault indicates that the inducer is not working properly. ... The fault is displayed when too much or too little current is detected on the inducer circuit.”

Documented for: (-)97V modulating furnaces

Likely causes, most common first

  1. Power outage
  2. Bad wiring to inducer
  3. Bad inducer
  4. Bad furnace control

What you can safely check yourself

  • Power cycle once at the furnace switch - the manual's own first solution is "Reset power to unit and clear fault", which clears the code after a brief power blip.

When to call a technician

If it does not clear on a reset, the inducer motor, its wiring or the control needs a technician.

Source

Rheem furnace code 77: No gas valve feedback signal

Hard lockout

No gas valve feedback signal. The furnace control has lost communication with the modulating gas valve. Gas heat is blocked; cooling still runs.

Manual wording: “NO GAS VALVE FEEDBACK SIGNAL ... This fault indicates that the gas valve is not working properly and has lost communications with the furnace control board.”

Documented for: (-)97V modulating furnaces

Likely causes, most common first

  1. Bad wiring to gas valve
  2. Bad gas valve
  3. Bad furnace control

When to call a technician

Technician only - gas valve wiring and replacement are never homeowner work.

Source

Rheem furnace code 93: Internal control fault detected

Hard lockout

Internal control fault detected. Either the control's own microprocessor self-test failed, or voltage was found on the main gas valve solenoid when there should be none. The furnace will not operate in any mode. The manual says this should rarely if ever be seen in the field.

Manual wording: “INTERNAL CONTROL FAULT DETECTED ... It is an indicator of an internal microprocessor fault on the furnace control (or I.F.C.) or voltage applied to the main gas valve solenoid when there should be none.”

Documented for: (-)97V, (-)96V, (-)801S/(-)801P

Likely causes, most common first

  1. 24VAC or similar voltage applied to the main gas valve solenoid circuit unexpectedly
  2. Furnace control software test failure - failed furnace control (or I.F.C.)

When to call a technician

Call a technician. This is either miswiring on the gas valve circuit or a failed control board, and it cannot be cleared by cycling the heat call.

Sources

Rheem furnace code 1: Soft lockout

Soft lockoutShown as: 1 blink of the green status LED, repeating

Soft lockout (one hour). On older Rheem/Ruud furnaces with a single green status LED, one blink means the control has locked gas heating out for an hour, normally after four failed ignition attempts. The manual's instruction is to reset system power and start over from the beginning.

Manual wording: “1 Blink - Soft lockout / Reset System power and start over from beginning”

Documented for: Standard (non-modulating, non-LXE, non-two-stage) furnaces with a green status LED, incl. RGRA/RGRB/RGTA/RGRS/RGTS/RGRT

Likely causes, most common first

  1. Four consecutive failed ignition attempts
  2. Flame proving problem - dirty or failing flame sense rod, igniter, or gas supply issue

What you can safely check yourself

  • Check that the gas shutoff to the furnace is on.
  • Check and replace a dirty air filter.
  • Reset power once at the furnace switch or breaker to clear the lockout.

When to call a technician

If the furnace locks out again, the ignition system (igniter, flame sensor, gas valve, gas pressure) needs a technician.

Sources

Rheem furnace code 2: Pressure switch circuit open - the switch failed to close

Soft lockoutShown as: 2 blinks of the green status LED, repeating

Pressure switch circuit open - the switch failed to close (or stayed open) when the inducer ran. Usually a blocked or over-long vent, a bad inducer, or a pressure switch hose problem.

Manual wording: “2 Blinks - PS Circuit open”

Documented for: Standard furnaces with a green status LED, incl. RGRA/RGRB/RGTA/RGRS/RGTS/RGRT

Likely causes, most common first

  1. Blocked vent, excessive vent length or elbows, or a restricted heat exchanger
  2. Pressure switch, pressure switch hoses or wiring fault
  3. Inducer not running or wired incorrectly
  4. Excessive wind opening the pressure switch
  5. Water or moisture in the switches and hoses

What you can safely check yourself

  • Go outside and check the vent and intake terminations for snow, ice, leaves or a nest.
  • On a 90+ condensing furnace, check the condensate drain and trap for a clog.
  • Reset power once at the furnace switch after clearing any blockage.

When to call a technician

If it returns, the inducer, pressure switch, hoses or vent run needs a technician. Never jumper a pressure switch.

Sources

Rheem furnace code 3: Limit circuit open

Soft lockoutShown as: 3 blinks of the green status LED, repeating

Limit circuit open. The high limit (or an auxiliary limit) has opened because the heat exchanger got too hot, which almost always means restricted airflow.

Manual wording: “3 Blinks - Limit circuit open”

Documented for: Standard furnaces with a green status LED, incl. RGRA/RGRB/RGTA/RGRS/RGTS/RGRT

Likely causes, most common first

  1. Dirty or clogged air filter restricting airflow
  2. Closed or blocked supply registers and return grilles
  3. Blower not running or running too slowly
  4. Faulty limit control or loose wiring

What you can safely check yourself

  • Check the air filter and replace it if dirty - this is the most common cause.
  • Open all supply registers and clear anything covering return air grilles.
  • Make sure the blower door is fully closed and seated.
  • Let it cool, then reset power once at the furnace switch.

When to call a technician

If three flashes come back after a clean filter and open registers, the blower, ductwork or limit control needs a technician. Never jumper or bypass the limit.

Sources

Rheem furnace code 4: Pressure switch circuit closed when it should be open - the switch is proving closed before the inducer starts

Safety faultShown as: 4 blinks of the green status LED, repeating

Pressure switch circuit closed when it should be open - the switch is proving closed before the inducer starts. The manual's checks are the pressure switch contacts, wiring shorts, the control, and water or moisture in the switches and hoses.

Manual wording: “4 Blinks - PS Circuit closed / - Check PS contacts - Check wires for short. - Check IFC. - Check switches and hoses for water or moisture”

Documented for: Standard furnaces with a green status LED, incl. RGRA/RGRB/RGTA/RGRS/RGTS/RGRT

Likely causes, most common first

  1. Pressure switch contacts stuck or welded closed
  2. Shorted wiring across the pressure switch
  3. Water or moisture in the switches and hoses
  4. Faulty integrated furnace control

What you can safely check yourself

  • Nothing safe for a homeowner here - a stuck-closed pressure switch is a combustion safety interlock that is not working.

When to call a technician

Call a technician. A pressure switch that will not open must be replaced, and any field jumper across it must be removed.

Sources

Rheem furnace code 5: Twin fault

WarningShown as: 5 blinks of the green status LED, repeating

Twin fault (optional feature). Applies only to furnaces wired together in a twinned pair. Rheem's own tech tip also notes the 5-blink code can appear in some cases when an electronic thermostat is used.

Manual wording: “5 Blinks - Twin Fault (Optional)”

Documented for: Standard furnaces with a green status LED and the twinning feature

Likely causes, most common first

  1. Twinning wiring or dipswitch setting between the two furnace controls is wrong
  2. The two transformers are not in phase, or the two controls are not the same part number
  3. On a single (non-twinned) furnace, TWIN not set to the single (OFF) position
  4. In some cases, an electronic thermostat can trigger this code

What you can safely check yourself

  • If you only have one furnace, note the code for your technician - it can point to a thermostat or dipswitch setting issue.

When to call a technician

Twin wiring, transformer phasing and dipswitch settings all have to be checked with power on - technician work.

Sources

How old is this Rheem?

Age changes what a fault code means for you. The same failure is a routine repair on a six-year-old unit and the end of the line on a twenty-year-old one. Your Rheem serial number has the build date in it.

Decode your Rheemserial number →

Manuals used for this page