an extra kick of the fan motor

My furnace blower contines to run for a couple of minutes after the heat cycle ends as it should, but when the fan motor shuts off, it immediately kicks back on for about a second and then kicks off and stays off until the next cycle. This seems to me to be hard on the motor. How can I get it to stop this?

 

If this is a typical home gas furnace (not sure about oil burners)...you might adjust the OFF limit on your fan down a few degrees.
A fan limit switch looks like this....


By adjusting the OFF limit down a bit, it will extract the last bit of heat out of the heat exchanger.

Once you find it, please post back before doing anything. Tell us what it is set to now. Adjusting it incorrectly can cause damage.

Posting the make and model of your furnace will help also.

 

My furnance is a 40,000 BTU Bryant Model # 394GAD024050
serial #0840A00166.

I cannot find a box on this furnance like the one in your picture.

 

The furnace model you have doesn't have that style fan control.


A description of your furnace is at:

http://xpedio.carrier.com/idc/groups...394g.25.2p.pdf



Under the heading "Standard Features" is an illustration of the Blower Control Center for your furnace. To get to it, you need to remove the fan compartment door.

The thermostat wires are connected to the circuit board. You need to remove two screws to get access to the circuit board.

If you have two relay in plastic cases on the circuit board, you will usually find an adjustable resistor with a white plastic dial on top of a black plastic case in the right rear of the circuit board

Turning the white plastic dial allows you to adjust how long the fan stays on. Turning the dial clockwise usually keeps the fan on longer.

 

Thanks SP...I knew one of you Pro's would be around to help out. Do you think that would solve the issue?

 

Usually an electronic fan control like the one you have wont turn the fan back on as you describe ---- while the mechanical fan control pictured by gunguy is famous for doing that just as he describes.

Give it a try and see what happens.

 

Are any wires connected to the "G" terminal on the circuit board?

 

I'm at work right now so I'll have to look at it again when I get home. I know that there at two wires a red one and a white one. But I'll have to look and see where the white one is connnected. I know the red one is connected to one of the r terminals.

I'll also look and see if I can find the adjustable resistor.

Thanks.

revjfk

 

I looked to see about the wires. The red one is connected to the "R" terminal. The white one is connected to the "w" terminal (go figure!) Anyway there is nothing hooked to any other terminal.

I was also unable to locate anything on the circuit board that looked to me like an adjustable resistor with a white plastic dial.

However, the good news is that the blower motor has stopped doing the extra kick back on and off. I don't know if it was something like the blower door not being seated properly before or maybe the blower motor just knew I was talking to experts and that it had better start behaving- But at any rate it is working correctly now!!

Thank you all for your help, and Merry Christmas!

revjfk