Coleman Furnace 13 Red Flashes
WarningShown as: Thirteen red flashes, then a two-second pause, repeating
The high-fire (second stage) pressure switch is open when it should be closed. The furnace cannot run on high fire, so on the coldest days it may not keep up.
Manual wording: “13 RED FLASHES: This indicates that the high-fire pressure switch is open when it should be closed. Check for a partially blocked vent pipe or a loose or disconnected wire before replacing pressure switch.”
Documented for: TM9V, TM8V, TMLV two-stage furnaces
Likely causes, most common first
- Partially blocked vent pipe
- Loose or disconnected pressure switch wire
- Faulty second-stage pressure switch
What you can safely check yourself
- Check the outside vent and intake pipe terminations for partial blockage from snow, ice, leaves or nests
When to call a technician
If the pipes are clear, the switch, hoses and inducer need to be tested with a manometer by a technician.
A Coleman furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- Installation Manual - Residential Gas Furnace, Models TM9V*MP (Two Stage Variable Speed ECM), 701379-UIM-B-1211 (Johnson Controls Unitary Products (Coleman), TM9V*MP two-stage variable-speed ECM gas furnaces) · checked 2026-08-25
- Installation Manual - Residential Gas Furnace, Models TM8V*MP, TMLV*MP - 80% AFUE (Two Stage Variable Speed ECM Multi-position / Low NOx), 643456-UIM-C-1211 (Johnson Controls Unitary Products (Coleman), TM8V*MP, TMLV*MP 80% AFUE two-stage variable-speed ECM gas furnaces) · checked 2026-08-25