Coleman Furnace 4 Amber Flashes (CP9C Echelon Modulating)
WarningShown as: Four amber flashes, two-second pause, repeating
The furnace has automatically cut back its heating output because airflow through the house side is restricted.
Manual wording: “Four Amber Flashes - Heating capacity is reduced due to restriction in the circulating air system. Check for dirty filter or closed registers.”
Documented for: CP9C Echelon modulating furnaces
Likely causes, most common first
- Dirty air filter
- Closed or blocked supply registers
What you can safely check yourself
- Check and replace the air filter
- Open all supply registers and clear anything blocking the return grille
When to call a technician
If the code stays after a clean filter and open registers, the duct system or blower needs a technician.
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