York P3HU - White-Rodgers - Continuous Flash

Article ID: 143
Last updated: 3 Nov, 2017

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


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
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Article ID: 143
Last updated: 3 Nov, 2017
Revision: 5
Access: Public
Views: 877
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