Flash Codes on York / Coleman Gas Furnace Board

FURNACE CONTROL BOARD DIAGNOSTICS
The furnace has built-in, self-diagnostic capability. If a system problem occurs, a blinking LED shows a fault code. The LED can flash red,green or amber to indicate various conditions. It is located behind a clear view port in the blower compartment door.

The control continuously monitors its own operation and the operation of the system. If a failure occurs, the LED will indicate the failure code. If the failure is internal to the control, the light will stay on continuously. In this case, the entire control should be replaced, as the control is not field repairable.

Flash sequence codes 1 through 11 are as follows: LED will turn on for 1/4 second and off for 1/4 second. This pattern will be repeated the number of times equal to the code. For example, six on flashes equals a number 6 fault code. All flash code sequences are broken by a 2 second off period.

Coleman / York Furnace Flash Code Chart

Flash Code	Result (Meaning)	Fix (Recommended Action)
Slow Green Flash	Normal operation	No action needed
Slow Amber Flash	Normal operation with call for heat	No action needed
Rapid Red Flash	Twinning error, incorrect 24V phasing	Check twinning wiring
Rapid Amber Flash	Flame sense current < 1.5 µA	Clean flame sensor, check gas flow, verify >1.5 µA at test pad
4 Amber Flashes	Y signal from thermostat without G signal	Correct thermostat wiring
1 Red Flash	Flame sensed with no call for heat	Check gas valve for leaks or slow closing
2 Red Flashes	Pressure switch stuck closed	Inspect/replace pressure switch, check wiring
3 Red Flashes	Pressure switch failed to close after inducer energized	Check inducer, vent pipe, hose, or pressure switch
4 Red Flashes	Limit switch open	Check filter, duct sizing, blower speed, firing rate, blower motor; also check fuse on board
5 Red Flashes	Rollout switch open	Reset rollout, check combustion air, inducer, heat exchanger, burners; cycle power after reset
6 Red Flashes	Pressure switch opened 4 times during heat call	Inspect pressure switch, venting, inducer; furnace locks out for 1 hr then retries
7 Red Flashes	Flame not established after 3 tries	Check gas pressure, gas valve, flame sensor, ignitor, burners
8 Red Flashes	Flame lost 5 times during cycle	Inspect gas pressure, flame sensor, gas valve
9 Red Flashes	Reversed line voltage polarity or grounding problem	Verify polarity, grounding, flame probe not shorted
10 Red Flashes	Flame sensed with no call for heat	Inspect gas valve and wiring
11 Red Flashes	Limit switch open >5 minutes (hard lockout)	Likely failed blower motor or wheel; cycle 24 VAC power after correction
12 Red Flashes	Open igniter circuit	Check for loose/disconnected wire or cracked igniter
Steady On Red	Control failure	Replace control board
60-Minute Auto Reset	Watchdog resets lockout after 60 minutes	Temporary protection; correct underlying issue
Flame Sense Levels	Normal ~3.7 µA DC; warning <1.5 µA; lockout <0.1 µA	Verify flame sensor current, clean/replace sensor if low