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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a mobile home furnace. It comes on for about 30 sec

Customer Question

I have a Coleman mobile home furnace. It comes on for about 30 sec and then shuts off. The burner is lighting fine.
The pilot light is staying lit. When the fan shuts off the burner stays lit.
The AC works fine and comes on and stays on when needed. When I turned the heat on
it started coming on and shutting off in 30 sec. Then doing it again in a few minutes.
I have replaced the thermocouple and the high & low switches.
I also replaced the fan switch but when I did that it wouldn't run at all so I had to put the old one back on.
It is still coming on only for about 30 sec and then shutting off.
Submitted: 1 year ago.
Category: HVAC
Expert:  airheatman replied 1 year ago.

Does the main blower ever start? And do you have a meter so we can troubleshoot?

Customer: replied 1 year ago.
the blower starts and shuts off after 30 sec. The burner flame stays on after the blower shuts off.
I do have a meter.
Expert:  airheatman replied 1 year ago.

OK lets put the meter leads on motor wires and see if the 120v is dropping out or if we still have power to motor when it quits.

Customer: replied 1 year ago.
ok...I will do that now
Customer: replied 1 year ago.
Where do you want me to put the leads to?
Expert:  airheatman replied 1 year ago.

I am looking but do not have a wiring diagram.If there is a wiring diagram take me a picture of the label where I can follow wires to motor and other components and paste picture here.

Customer: replied 1 year ago.
Here it is, hope you can open it.
Expert:  airheatman replied 1 year ago.

Excellent job. Thanks. First we will check between the high voltage wire at transformer where blower gets power and the side of the fan switch towards motor

Customer: replied 1 year ago.
Tested the fan switch and it is 121
Expert:  airheatman replied 1 year ago.

Is that same as here where you are testing?

Customer: replied 1 year ago.
Can you pinpoint from this where I need to test.
Expert:  airheatman replied 1 year ago.

Not really.I can not tell what goes or comes from where in pic. But it should be where to fan wires connect.We want to know if fan is getting power at time it stops.

Customer: replied 1 year ago.
Let me resend this
Expert:  airheatman replied 1 year ago.

OK

Customer: replied 1 year ago.
Also the burner is staying on once fan shuts off...should it be like that?
Customer: replied 1 year ago.
Did they come through ok?
Expert:  airheatman replied 1 year ago.

Follow the fan wires from motor and show me where the hook up. Burners should shut down within a minute if fan stops.

Expert:  airheatman replied 1 year ago.

I can see pics, but unable to race to motor

Customer: replied 1 year ago.
If I test the fan wire there is voltage, If I test the wire where the line comes in from motor there is voltage.
If I test them together there is no voltage.
Customer: replied 1 year ago.
Will anyone be able to respond today?
Customer: replied 1 year ago.
Anybody willing to help me???