York Furnace Continuous Amber Flash
WarningShown as: Amber LED flashing on and off continuously with no pauses
The flame sense current has fallen below 1.5 microamps. The furnace is still lighting, but the control can barely see the flame and will eventually lock out if the signal keeps dropping.
Manual wording: “CONTINUOUS AMBER FLASH: Flame sense current is below 1.5 microamps. Check and clean flame sensor. Check for proper gas flow.”
Documented for: TG8S, TG9S, TM9V, TM9Y and other UPG boards. On TM8Y the threshold is 0.28 microamps.
Likely causes, most common first
- Dirty or corroded flame sensor rod
- Poor gas flow to the burners
- Weak or failing flame signal path
What you can safely check yourself
- Replace a dirty air filter
- Make sure the vent and combustion air pipes outside are clear of snow, ice, leaves or nests
When to call a technician
Cleaning the flame sensor means working inside the burner compartment with the gas on. Have a technician clean the sensor and measure the flame current. Ignoring it usually ends in a no-heat lockout.
A York furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- Installation Manual - Single Stage PSC Residential Gas Furnaces, TG9S and GG9S Series (95.5% AFUE Multi-position), 1083287-UIM-A-0114 (Johnson Controls Unitary Products (York), TG9S*MP, GG9S*MP single-stage PSC 95.5% AFUE gas furnaces) · checked 2026-08-25
- Installation Manual - Single Stage PSC Residential Gas Furnaces, TG8S*MP / TGLS*MP / GG8S*MP / GGLS*MP (80% AFUE Multi-position / Standard Low NOx), 998491-UIM-B-1013 (Johnson Controls Unitary Products (York), TG8S*MP, TGLS*MP, GG8S*MP, GGLS*MP 80% AFUE single-stage gas furnaces) · checked 2026-08-25
- Installation Manual - Two Stage Variable Speed ECM Residential Gas Furnaces, TM9V Series (96% AFUE Multi-position), 1083294-UIM-A-0114 (Johnson Controls Unitary Products (York), TM9V*MP two-stage variable-speed ECM 96% AFUE gas furnaces) · checked 2026-08-25