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I have Coleman Presidential model 7970-656/D hot surface ignition that I'm having problems with that I hope I can describe correctly. I hear the thermostat click, the combustion fan motor will come on, I see the igniter glowing, the valve will click and the gas will ignite and after that the problem starts. Then the gas valve will click and the flame dies then the valve goes on and off several times like it cant make up it's mind. The valve will finally come on, the gas will ignite and I'll get some heat. I've replaced all the limit switch's, transformer and ignition module and it didn't make a bit of difference. Is there some sort of pressure switch in the combustion fan motor or some place else that could be bad?

Thanks
Mike

Hi Mike,

You would have to look at wiring diagram and trace the circuits with a meter at time of problem to locate interruption.


Your hot surface ignitor also serves as a flame sensor.

That could be faulty and shutting gas down. Could be intermittant also, which makes it harder to find.

It could be the gas valve itself, a short in wiring also.


Too many variations to know other than testing one by one to locate.



Thanks for inquiring,
Robert

Thanks Robert..

You're very welcome, happy to help.




Take care and best wishes,
Robert