York P3HU - White-Rodgers - Continuous Flash

York Gas Furnace: P3HU

Re: White-Rodgers 50A50-241 - Rapid Flash / Flashing Continuous

Rapid Flash = Flame sensed with no call for heat.

In a Rapid Flash situation, the furnace control board thinks that the gas valve is stuck on and flame is still burning without a call for heat. Therefore, when a control board goes into a code 1, it will lock the inducer motor and blower motor on.

Qty	Possible Causes (From Most to Least Likely):
	Bad Control Board
	Sticking Gas Valve
	Shorted Flame Sensor

CHECKOUT:

1. Check Gas Valve

Start the furnace with a call for heat
After the burners have been lit for at least 30 seconds, remove the "W" wire.
- The burners should extinguish immediately.
  - Delayed shut-off = Sticking Gas Valve

2. Check Flame Sensor

Visually check the flame sensor for rust or other items that may cause a false reading.
Check flame sensor Microamps with the burners off.
- No Microamp signal but controller locks-out = Bad Control Board