heating problem

[LarryM2]

Have a rheem RGDJ-07EAUER gas hot air furmace. The heat comes on but the blower doesnt. The blower in the fan position on the thermostat runs so it seems its not the blower itself. Any help would be greatly appreciated.

[HayZee518]

check for any plenum switches in and around the heating chamber of the furnace. most look like a device about the size of a nickel with two or more spade connectors on it. usually a surface mounted device.

[hvacwiz]

If your furnace has a circuit board, your problem lies there.

[gerryc]

the furnace manual/documentation has a flowchart of the furnace startup. In our rheem criterion, before the fan is turned-on, the system has to detect presence of the flame. There maybe a flame sensor that needs to be cleaned.

[jnaas2]

Hvacwiz Has the answer if the furnance has a circuit board after it gets the signal from the flame sensor that the burners have been lit it will turn on the fan after a set amount of time usually about 30 seconds. If the furnance doesnt have a circuit board then it has a old fashioned fan control in the bonnet that has a dial on it with temperature to adjust the on setting for the fan and off and also a high temperature setting that shuts down the burner. The fan on and auto is controled different then the heat cycle