Ruud Furnace Code 23
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
- 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.
A Ruud furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- Installation Instructions for Upflow Condensing Modulating, Communicating Gas Furnaces - (-)97V Series (92-24161-126-04) (Rheem Manufacturing Company (Ruud brand), U97V series modulating condensing gas furnace (and U98V); TABLE 18 normal operation codes, TABLE 19 fault codes, pages 94-104) · checked 2026-08-25
- Installation Instructions for 4 Position Condensing Two-Stage, Communicating Gas Furnaces - (-)96V Series (92-24161-124-08) (Rheem Manufacturing Company (Ruud brand), U96V series and (-)(-)96MDV two-stage condensing gas furnaces; TABLE 19 normal operation codes, TABLE 20 fault codes, pages 111-120) · checked 2026-08-25
- Fault Codes (furnace control fault-code label) 92-103343-01-00 (Rheem Manufacturing Company (Ruud brand), Rheem/Ruud communicating integrated furnace control (IFC) fault-code label applied inside the furnace door) · checked 2026-08-25