Gas and Oil Home Heating Furnaces - whats the problem

My furnace, a heil, circa 1988, lights for about a minute, then turns off for two to three minutes then repeats over and over again. All the while the fan keeps on blowing. Any advise would be appriciated. Had a guy in today who said the heat exchanger is shot and the entire unit should be replaced. Just dont want to do that if its not needed.

I have had this problem on a couple different occasions with a couple of different causes and solutions.

1st time turned out to be the limit switch (trips when the heat in the plenum gets too hot); had to replace it.

2nd time turned out to be that the flame sensing rod needed to be sanded, so that it could tell there was a flame. It may build up over time.

I'm not sure what your solution will be, but these are a couple things in which to take a look.

Upon what did he base his conclusion? Did he show you a crack or hole in the heat exchanger?

I have an old payne forced air furnace, and the pilot is lit, we have tested the tstat, tried jumping the tstat, checked all wires, and still nothing is happening. Could this be the gas valve or something else?

Model #?

Chances are, the flame sensor may be dirty.. (If you have one, we need to know the model before we jump the gun)

zman,

Have you made sure your cold air return grills are clear to pass air good and you have a clean filter?, and that too many registers in the heat vents are not closed down or blocked? These things always need to be looked at first, with your symptoms.

Some people here have experimented and left off the blower compartment door, held in the safety switch (called an interlock switch), and ran the furnace and then found the furnace no longer shuts down intermittently, as a clue.

janelle,

You should have started your own thread, IMO.

I have an old payne forced air furnace, and the pilot is lit, we have tested the tstat, tried jumping the tstat, checked all wires, and still nothing is happening. Could this be the gas valve or something else?

Yes it could be the gas valve or it could be something else. It could be the control transformer or possibly a fuse in the control transformer secondary circuit. It could even be the combination gas valve selector is in the pilot position instead of the on position.

Do you have a multimeter?

Another thing I thought of a person should readily do with furnaces acting up, as this is so easy, is to make sure the condensate lines are clear by blowing into them each way. A back up of condensate can produce continous or sporadic issues with the furnace running and not running.

Also, in my experience with Heils, the ventor fan can come loose or fall off inside due to the corrosive nature of the condensate water. (The Heils I worked on had the ventor laying horizontally with the fanblade hanging down, and relied heavily on this metal spring clip inside to hold it tight to the shaft. The spring clips rot away.) So you want to make sure the ventor is not unusually noisy and that it is venting properly to the point the pressure switch is not operating on the cusp of it being "closed" or not.

HELLO!


It's a lot more important to determine whether the heat exchanger is cracked than to get the furnace working. If you don't trust the report you got of that defect, call another service agency and have them show you the cracks or the method they use to diagnose the problem.

Another way of getting a service agency to pay attention is to point out that if you replace the furnace on their say-so, and an inspection of the heat exchanger reveals there is no crack, hole or defect, that they are on the hook for the damages caused by their bum diagnosis.


Find an outfit you trust to provide you with honest and competent service. Those are the priorities you should look for in hiring service agencies, in my opinion.