I searched these forums but couldn't find my problem.
I have a York Diamond 80 (about 20 years old)
model #P3HUA12L04801A
The furnace runs through its normal heat cycle. Once it reaches temperature it shuts down except for the main blower. It continues to blow cold air through the house until I cycle power to the furnace.
When the furnace is blowing cold air after the heat cycle the control board LED flashes continuously. The control board cover indicates this is FLAME - NO CALL FOR HEAT. I checked the high limit switch and it is working as it should.
What else should I check?
Thanks

 

Most furnace controls continue to power the blower after the thermostat is satisfied since there is still usable residual heat in the furnace's heat exchanger. I would think this cool down function termination is adjustable by changing time or temperature at the control board.

 

Hi beelzebob,
Thanks for the reply. Yes, but the blower continues to run until I remove power from the furnace. When I reapply power the blower is off until the temp drops below the setpoint.

 

When you cycle power right after the thermostat is satisfied, the blower should be running until the time period has elapsed or the heat exchanger temperature is decreasing below the blower OFF setpoint depending on which design your furnace control has.

 

The blower will run for hours blowing cold air if I don't cycle power.

 

That is not what you said in post #3.

 

Sorry for the confusion. I said in post #3, "the blower continues to run until I remove power from the furnace." I should have been more clear and said the blower continues to run after the heating is finished until I remove power from the furnace.

 

Welcome to the forums.

If that is the original control board in that furnace...... then the blower is timer controlled.
If it's not shutting off..... the board has a problem.