Coleman Furnace 1 Green Flash (CP9C Echelon Modulating)
StatusShown as: One green flash, two-second pause, repeating
Normal operation with no call for heat. Standby.
Manual wording: “One Green Flash - Normal Operation with no call for heat.”
Documented for: CP9C Echelon modulating furnaces
Likely causes, most common first
- Normal standby
What you can safely check yourself
- If the house is cold, check the thermostat is set to HEAT and above room temperature
When to call a technician
No service needed.
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