PBKM furnace Propblem?

Question

I have an electronic PBKM furnace model "A" that once in a while when the burner cycle turns off the blower will continue running until air gets cold. I tried limit switches, flame sensors, limit flame switch..You neme it I did it.The last thing I found was that the door switch was stock on close circuit possition. After I disconected it, blower went off. I by-passed the switch. But seems to be that this switch has also an automatic shut off funtion after the cycle is completed. Tell me if I have to install a new switch for normal cycle run.

Answer 1

I believe this furnace has a control board which is what controls the timing of the fan in heat mode. You may have a problem with a relay on the board itself. In any case, as gas man said, it's best to call a professional.

Answer 2

There is a slide switch time delay off on the circuit board . Look at the schematic of the COMPUTER board to find it . Most of them have a 90 sec, 120 sec, off time . Find it and set it . Most furnaces that you cant get the blower to turn off means the COMPUTER is bad . Especially with carrier.

Answer 3

after 38 years as a master hvac tech i can tell u my best advice is to call a good pro,,it will save u money in the long run and give u peace of mind,,i have seen to many people throw parts at at problem that could be fixed by a pro for 1/2 the $$$ ,

Answer 4

what "gas man" said!