Coleman Furnace Steady On Red (CP9C Echelon Modulating)
Hard lockoutShown as: Red LED lit solid, not flashing
A control fault has been detected, or 24 volts is present without 115 volts.
Manual wording: “Steady On Red - Control fault has been detected or there is 24 volts present without 115 volts. Check that there is 24 volts and 115 volts being supplied to the board. If so, then the board should be replaced.”
Documented for: CP9C Echelon modulating furnaces
Likely causes, most common first
- Missing 115 volt supply to the board
- Failed control board
What you can safely check yourself
- Check the furnace breaker in the electrical panel is on
- Turn the furnace off at the service switch for a minute, then back on once
When to call a technician
If both 24V and 115V are present and the LED is still solid red, the board has to be replaced. Voltage checks and board replacement are technician work.
A Coleman furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Source
- Installation Manual - Residential Gas Furnace with ECM Motor, Models TP9C*C, YP9C*C, CP9C*C, LP9C*C (Up to 98% Modulating Multi-position), 681292-UIM-B-1211 (Johnson Controls Unitary Products (Coleman), CP9C*C Coleman Echelon modulating gas furnace (manual also covers the identical TP9C, YP9C and LP9C chassis)) · checked 2026-08-25