Carrier Furnace: 1 Flashes
A Carrier furnace LED pattern starting with 1 flashes matches 8 documented codes: 10.1, 11, 12, 13, 14, 14.2, 14.3, 15. Watch the full pattern (short vs. long flashes) to tell them apart — all 8 are explained below.
Code 10.1: L1 polarity fault
L1 polarity fault. The polarity of the incoming 115 V power is reversed and the furnace will not operate.
Manual wording: “10.1 L1 POLARITY FAULT - Rapid flash LED. Polarity of incoming 115V power is reversed.”
Documented for: 58SC0B/58SC1B
Likely causes, most common first
- Line voltage (115 V) hot and neutral reversed at a junction
- If units are twinned, improper low-voltage (24 V) transformer phasing
When to call a technician
Correcting 115 V polarity means opening junction boxes and working on live wiring - call a licensed HVAC technician or electrician.
A Carrier furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Source
- Installation, Start-Up, Operating and Service and Maintenance Instructions - 58SC0B/58SC1B (Carrier, 58SC0B/58SC1B single-stage condensing gas furnace with 3-digit status display) · checked 2026-08-25
Code 11: No previous code
No previous code. The control has no fault stored - either nothing has failed or the stored code has aged out. Stored codes erase automatically after 72 hours.
Manual wording: “11 NO PREVIOUS CODE - Stored status codes are erased automatically after 72 hours or as specified above.”
Documented for: 58SC0A, 58MCB, 58MVP, 58UVB and most Carrier 58-series furnaces
Likely causes, most common first
- Normal - no fault in memory
- A previous fault was cleared by a power interruption or by the 72-hour timeout
What you can safely check yourself
- Nothing to fix - run the furnace through a full heating cycle and see whether a real code appears
When to call a technician
If the furnace is misbehaving but only shows 11, have a technician watch a live heating cycle to catch the fault as it happens.
A Carrier furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- Troubleshooting Guide - Variable Speed, Two-Stage Gas Furnaces (Form 58-06T) (Carrier, 58MVP, 58UVB and other Carrier variable-speed two-stage gas furnaces (replaces 58MVP-10SM)) · checked 2026-08-25
- Installation, Start-Up, Operating and Service and Maintenance Instructions - 58SC0A/58SC1A (Carrier, 58SC0A/58SC1A single-stage 4-way multipoise condensing gas furnace) · checked 2026-08-25
- 58MCB 4-Way Multipoise Fixed-Capacity Condensing Gas Furnace - Service Manual (Carrier, 58MCB single-stage condensing gas furnace) · checked 2026-08-25
Code 12: Blower on after power up
Blower on after power up. Normal operation - if furnace power is interrupted and restored while the thermostat is calling for heat, the blower runs for 90 seconds.
Manual wording: “12 BLOWER ON AFTER POWER UP - (115 VAC or 24 VAC) - Blower runs for 90 seconds, if unit is powered up during a call for heat (R-W/W1 closed)”
Documented for: 58SC0A, 58MCB, 58MVP, 58UVB and most Carrier 58-series furnaces
Likely causes, most common first
- Power was interrupted and restored during a call for heat (R to W closed)
- The thermostat call ended during the blower on-delay period
What you can safely check yourself
- Nothing to fix - this is normal after a power blip or after you flip the furnace switch back on
When to call a technician
If code 12 keeps appearing without any power outages, have a technician check for a loose 115 V connection or a failing door switch.
A Carrier furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- Troubleshooting Guide - Variable Speed, Two-Stage Gas Furnaces (Form 58-06T) (Carrier, 58MVP, 58UVB and other Carrier variable-speed two-stage gas furnaces (replaces 58MVP-10SM)) · checked 2026-08-25
- Installation, Start-Up, Operating and Service and Maintenance Instructions - 58SC0A/58SC1A (Carrier, 58SC0A/58SC1A single-stage 4-way multipoise condensing gas furnace) · checked 2026-08-25
- 58MCB 4-Way Multipoise Fixed-Capacity Condensing Gas Furnace - Service Manual (Carrier, 58MCB single-stage condensing gas furnace) · checked 2026-08-25
Code 13: Limit circuit lockout
Limit circuit lockout. The limit switch, draft safeguard, flame rollout, or blocked-vent switch has stayed open longer than 3 minutes (or the furnace tripped the limit 10 times in a row on high heat). The control locks out and auto-resets after 3 hours.
Manual wording: “13 LIMIT CIRCUIT LOCKOUT - Lockout occurs if the limit, or flame rollout switch is open longer than 3 minutes or 10 successive limit trips occurred during high-heat. Control will auto reset after 3 hours.”
Documented for: 58SC0A, 58SC0B, 58MCB, 58MVP, 58UVB
Likely causes, most common first
- The furnace repeatedly overheated - almost always an airflow problem (see code 33 for the full cause list)
- Flame rollout switch tripped, which requires manual reset by a technician
- Defective limit switch or connections
What you can safely check yourself
- Check the air filter and replace it if it is dirty - restricted airflow is the number one cause
- Make sure supply registers and return grilles are open and not blocked by furniture or rugs
- Check that the furnace door is fully closed
When to call a technician
Code 13 means the furnace has been overheating. Even if a new filter clears it, have a technician verify why the limit was tripping - a flame rollout trip in particular is a combustion problem that must be diagnosed before the furnace is put back in service.
A Carrier furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- Troubleshooting Guide - Variable Speed, Two-Stage Gas Furnaces (Form 58-06T) (Carrier, 58MVP, 58UVB and other Carrier variable-speed two-stage gas furnaces (replaces 58MVP-10SM)) · checked 2026-08-25
- Installation, Start-Up, Operating and Service and Maintenance Instructions - 58SC0A/58SC1A (Carrier, 58SC0A/58SC1A single-stage 4-way multipoise condensing gas furnace) · checked 2026-08-25
- Installation, Start-Up, Operating and Service and Maintenance Instructions - 58SC0B/58SC1B (Carrier, 58SC0B/58SC1B single-stage condensing gas furnace with 3-digit status display) · checked 2026-08-25
Code 14: Ignition lockout
Ignition lockout. The furnace failed to ignite the gas and prove flame in four attempts. The control locks out and auto-resets after 3 hours.
Manual wording: “14 IGNITION LOCKOUT - System failed to ignite gas and prove flame in 4 attempts. Control will auto-reset after 3 hours. See status code 34.”
Documented for: 58SC0A, 58MCB, 58MVP, 58UVB
Likely causes, most common first
- Igniter or flame sensor problem (see code 34 for the manual's full list)
- Low inlet gas pressure or a closed manual gas valve
- Defective gas valve
- Loss of control ground continuity
What you can safely check yourself
- Confirm other gas appliances in the house are working, so you know the gas supply itself is on
- Turn the furnace off at the service switch for a minute and back on once to force one clean retry
When to call a technician
Ignition lockout is a gas-side fault. Diagnosing the igniter, flame sensor, gas valve, and gas pressure requires a technician - do not attempt to clean or move the flame sensor yourself.
A Carrier furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- Installation, Start-Up, Operating and Service and Maintenance Instructions - 58SC0A/58SC1A (Carrier, 58SC0A/58SC1A single-stage 4-way multipoise condensing gas furnace) · checked 2026-08-25
- Troubleshooting Guide - Variable Speed, Two-Stage Gas Furnaces (Form 58-06T) (Carrier, 58MVP, 58UVB and other Carrier variable-speed two-stage gas furnaces (replaces 58MVP-10SM)) · checked 2026-08-25
Code 14.2: Flame lost lockout
Flame lost lockout. The flame signal was lost three times after the heating blower on-delay. The control auto-resets after 3 hours.
Manual wording: “14.2 FLAME LOST LOCKOUT - Flame signal was lost 3 times after heating blower on delay. Control will auto-reset after 3 hours. See status code 34.3.”
Documented for: 58SC0B/58SC1B
Likely causes, most common first
- Incorrect manifold pressure or gas firing rate
- Gas inlet pressure fluctuations
- Flame sensing problem - see code 34
What you can safely check yourself
- Check that the furnace filter is clean and vents are open, since airflow problems can disturb the flame
When to call a technician
Losing an established flame repeatedly is a combustion problem. Have a technician check manifold pressure, gas supply pressure, and the flame sensing circuit before running the furnace.
A Carrier furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Source
- Installation, Start-Up, Operating and Service and Maintenance Instructions - 58SC0B/58SC1B (Carrier, 58SC0B/58SC1B single-stage condensing gas furnace with 3-digit status display) · checked 2026-08-25
Code 14.3: Flame lost lockout
Flame lost lockout. The flame signal was lost seven times during a single heat request.
Manual wording: “14.3 FLAME LOST LOCKOUT - Flame signal was lost 7 times during a single heat request. See status code 34.2 to 34.3.”
Documented for: 58SC0B/58SC1B
Likely causes, most common first
- Incorrect manifold pressure and gas firing rate
- Gas inlet pressure fluctuations
- Flame sensing problem - see codes 34.2 and 34.3
What you can safely check yourself
- Check that the furnace filter is clean and supply and return vents are open
When to call a technician
Repeated flame loss inside one heat call needs a technician to check gas pressure and the combustion setup. Do not keep resetting the furnace to force it to run.
A Carrier furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Source
- Installation, Start-Up, Operating and Service and Maintenance Instructions - 58SC0B/58SC1B (Carrier, 58SC0B/58SC1B single-stage condensing gas furnace with 3-digit status display) · checked 2026-08-25
Code 15: Blower motor lockout
Blower motor lockout. The variable-speed blower failed to reach 250 RPM, or failed to communicate with the control within 30 seconds of being switched on, in two successive heating cycles. Auto-resets after 3 hours.
Manual wording: “15 BLOWER MOTOR LOCKOUT - Indicates the blower failed to reach 250 RPM or the blower failed to communicate within 30 seconds after being turned ON in two successive heating cycles.”
Documented for: 58MVP, 58UVB and other variable-speed two-stage Carrier furnaces
Likely causes, most common first
- Failed blower motor or motor control module
- Loose or damaged blower motor wiring/communication harness
What you can safely check yourself
- Check that the blower door is fully seated - the door switch removes power to the blower
When to call a technician
A variable-speed blower motor fault is a technician job; the motor, its module, and its harness all have to be tested.
A Carrier furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Source
- Troubleshooting Guide - Variable Speed, Two-Stage Gas Furnaces (Form 58-06T) (Carrier, 58MVP, 58UVB and other Carrier variable-speed two-stage gas furnaces (replaces 58MVP-10SM)) · checked 2026-08-25