York Diamond 80 P4HUA12N06401A

[Dallas Wilm]

I just bought a house and it has a York Diamond 80 P4HUA12N06401A furnace. I am unfamiliar with this make/model and am just wondering if the fan is supposed to run continuously as this one does.

I found that if I cranked the thermostat to max and watched, the furnace will ignite and run for about 20 minutes and then shut off. Then when I return the thermostat to normal it seems that the fan cuts in and then just runs forever without heat until I crank it to max again.

The old mercury thermostat doesn't appear to have a fan control on it just temperature.

Is this a problem with the furnance or the thermostat?

[RegUS_PatOff]

Thermostat model number ?

[jb8103]

I just bought a house and it has a York Diamond 80 P4HUA12N06401A furnace. I am unfamiliar with this make/model and am just wondering if the fan is supposed to run continuously as this one does.

I found that if I cranked the thermostat to max and watched, the furnace will ignite and run for about 20 minutes and then shut off.

You mean the furnace shuts off before the thermostat is satisfied? Does the blower come on during this twenty minute period?

Then when I return the thermostat to normal it seems that the fan cuts in and then just runs forever without heat until I crank it to max again.

So the blower comes on again after you turn down the thermostat?

[applianceman18007260692]

Post some photos so we can see what you have

[ACtechGUY]

Almost all furnaces have the ability to run the fan continuously. There is a tap on the control board in the furnace for continuous fan speed . That being said I think you should look at the thermostat and unscrew the thermostat (mercury section) from the base section and inspect it. look for the fan switch that may have been snapped off . Next look for a teminal marked G . Take that wire off. The fan should stop within 2 minutes (or immediatly) . If the fan still runs the problem is probably the fan speed tap in the furnace.