Goodman furnace C: Compressor cooling with a single stage compressor
A plain C means the furnace is running its blower for cooling with a single stage compressor. It is a status indication, not a fault.
Applies to: Goodman GMVM97, GCVM97 and Amana AMVM97 modulating gas furnaces with a two-character display, set up with a single stage outdoor unit.
What it means
The furnace houses the indoor blower that the air conditioner depends on, so its display reports cooling as well as heating. The character shown depends on how the outdoor unit is configured. A plain C means the control is set up for a single stage compressor, so there is only one cooling capacity to report. C1 and C2 mean the same thing on a two stage system, low and high. Someone reading C on one furnace and C1 on another has not found a difference in fault status — the two furnaces have different outdoor units.
Most common causes
- The thermostat is calling for cooling, which is the normal reason.
- The furnace is configured for a single stage outdoor unit rather than a two stage one.
- The blower is running on the cooling speed, which is the furnace's role during a cooling call.
How to diagnose it
- Note whether the house is cooling. If it is, there is nothing to diagnose.
- If the blower runs but no cool air arrives, the fault is in the outdoor unit or the refrigerant circuit, not in this code.
- A furnace showing C where you expected C1 or C2 is configured for a single stage compressor. That is a setup difference, not a fault.
How to fix it
- Nothing. This is normal operation.
- If cooling performance is the complaint, the furnace is reporting that its part is working — look at the outdoor unit.
Notes
The single character codes on this display are easy to mistake for fault codes because they are short and unfamiliar. On this control the fault codes are the ones that spell something out, like IF for an internal control fault.
Related
All codes for this manufacturer
Goodman and Amana furnace fault codes — every code, with what differs between models.