djh860

Hi this has been an occasional problem but now it is to the point that the furnace wont keep burning.
When switched on it lights normally. They about 3 seconds later it cuts out. I'm sure its a sensor. How can we figure out which one is signaling a problem?
Also what might the problem be? I mean could it be a bad sensor or does it mean something major? It has been running very strong. I think it may have to do with condensation.

kok328

Any trouble code lights flashing on the circuit board?
Have you been able to Ohm out any limit switches?

djh860

No its too old for that no computer read out or indicator lights

kok328

Can't say for sure but, I'd try replacing the thermocoupler.

djh860

Today I discovered that the flame at ignition is not getting all the way across to the last burner. The ingition sensor is at the last burner. Since it does not detect flame it shuts down the system. Any one know why this might be happening? Could it be having problem drawing air. Could the elements be bad?

kok328

Possilby an obstruction in the gas manifold tube. Typically this would be a spider nest/web of some sort. See if you can rod out the tube across the burners and see if that provides a fix.

baldy

a volt meter will tell all ....find out what the ohms is on the sensor and it tell you what the min.is ,,,