TM9T Diagnostic Codes / Fault Codes

York Gas Furnaces: TM9T

Re: Diagnostic Codes / Fault Codes

These York gas furnaces have a control board inside the furnace blower compartment that will flash a diagnostic code that shows the operating status of the furnace.

Diagnostic Codes:
Slow Green	Normal Operation - no call for heat
Slow Amber	Normal Operation - with a call for HEATING
Rapid Amber	Low flame signal	Flame signal below 1.5 microamps Check flame sensor Check gas pressure
4 Amber	No Call for G.	Check low voltage wiring
Rapid Red	Twinning error; incorrect phasing	Twinned furnaces must be on the same "phase" of power. Check voltage between the "Hot" legs of power of each furnace - should read 0 volts.
1 Red	Flame present with gas off	Stuck gas valve Shorted flame sensor Faulty control
2 Red	Pressure switch stuck closed	Bad pressure switch Inducer fan relay stuck on
3 Red	Pressure switch stuck open	Bad pressure switch Bad inducer fan Bad inducer fan relay Blocked or restricted vent Condensate drainage issue
4 Red	Limit switch open / open fuse	Bad limit Low airflow Over-Fired
5 Red	Rollout switch open / open fuse	Bad switch Cracked heat exchanger Bad inducer motor Over-Fired
6 Red	4 open pressure switch faults in one heating cycle	Bad pressure switch Bad inducer fan Bad inducer fan relay Blocked or restricted vent Condensate drainage issue
7 Red	3 failed ignition attempts	Bad igniter Dirty flame sensor No gas flow
8 Red	Flame was established but later lost - 5 times in one heating cycle	Dirty flame sensor Combustion air problem
9 Red	Grounding or line polarity fault	Look for loose or missing Ground wire Try reversing transformer power
10 Red	Gas valve circuit shorted	Check gas valve wiring
11 Red	Extended limit switch open	Bad limit Blower failure
12 Red	Igniter failure	Bad Igniter Bad board

Fault Code Retrieval: With no thermostat call push and release the LAST ERROR button. The LED will flash up to 5 stored fault codes, beginning with the most recent. If there are no codes in memory, the LED will flash two green flashes.

Clear the Fault Codes: Push and hold the LAST ERROR button for at least five seconds. The LED will flash three green flashes when the memory has been cleared.