I have an older(late 80s) forced air Amana Air Command 80 furnace that intermediately fails to light. Everything seems to work correctly till the gas is released to the burners ...then it doesnt fire and it shuts the gas and ignitor down...it will recycle and try a second time(sometimes works) and fails at the same point....then the evacuation fan continues to run until I shut the unit down and try to restart again ...it usually lights at this point.

Seems to occur most often after a setback where everything cools down but has failed at other times too. Its been doing this for a couple of seasons but seems worse lately.

Again it seems to work as it should until the gas release to burner...evac fan comes on, match lights(glows orange), gas releases...no fire within 3 sec = shutdown match and gas....tries a second time...shutdown...evac continues to run till manually shut off.

Any ideas....gas valve? ...gas pressure?

Thanks

 

If you have gas at the burners, more than likely it's a weak ignitor or dirty burners.

 

Thanks, I was just inspecting the ignitor and it does look like its deteriorated some....Ill order a new one.

Any suggestion on best way to clean the burners.

Thanks again.

 

I am ultimately having the same condition as you but there may be one big difference. In my case, I don't think that the gas valve is even opening up, which would steer one away from dirty burners or week igniters. When resetting the unit, like you mentioned; The furnace completes the following steps when it works:
1. The exhaust fan comes on 2. The igniter starts to glow 3. I hear a distinct click of a relay and then hear the flow of the gas 4. The gas ignites and the burners light 5. The blower kicks on.
When it is not working STEP #3 is missed and it appear to abort the process, and then trys again when like you, it may or may not work.

My point is, it see less likely that the gas is not igniting and more likely that the control that turns on the gas is intermittently not working.

I encourage you to listed for this (assuming your furnace has some discernible sounds to let you know when the gas turns on). If you DO hear it turn on and it doesn't light, then maybe the advice you have received is correct. If however, it is like my situation, the gas is not even flowing when the trouble occurs and the problem is therefore not dirt burners or weak igniters.



By the way, should I repost my problem as a new thread, or do you think people will answer my reply to yours here?

 

Reposting to a new thread makes things a lot simpler.

 

jd....I do here the gas valve cycle and do actually hear and smell the gas....after about 3 sec the fail safe will shut the gas and ignitor off if it fails to light.....so Ill try a new ignitor and see what happens.

Sad thing is ...I have a brand new 93% Goodman unit that I havnt installed. No body wanted to install it for me so Ill have to do it myself in the spring. With the economy being down maybe I should make a few calls again as some may be willing to do the job now.

 

Installing furnaces is attractive because of the substantial markup on the materials sold.

Just selling labor to install the equipment isn't nearly as attractive, and you buy yourself issues if the equipment chosen isn't suitable, the furnace doesn't work, parts are bad or whatever.

Buy your own furnace, expect to install it yourself.

Of course if you can find someone to do that for you that's certainly fine. It's just likely to be a lot less attractive for a quality installer.

 

Yeah the plan all along was to install myself.....just need to get off my bum and git r done

 

A weak ignitor was indeed the problem

 

Thanks for lettung us know, since this is one of those things were some people might think the old 'weak ignitor' bit, is some sort of theory. It's not.

 

No problem....ignitors are relatively cheap, easy to replace and you can always use an extra one even if that wasnt the problem.

Great discussion board!