Burners won't light in older furnace

[tysonjm]

I've got a Magic Chef furance/blower from the early '80s. When the thermostat calls for heat, an ignitor starts clicking and a steady pilot light comes on. The clicking will continue for about 10-15 seconds, then stop. After another 5 seconds, a different click is heard (gas shutting off?) and nothing happens but the pilot light stays lit. I did see one time, during the initial clicking, the two burners fire up fully only to poof off after about 5 seconds. The furnace had been working fine when we used it once or twice a week over the last month.

After some research, it appears the pilot light is lighting just fine, but perhaps the flame sensor is dirty or bad? I'm not able to tell where the the flame sensor is in this model to check though. Any other ideas on why the burners won't light? I know this is one is old and probably either needs cleaning and/or replaced. Here are a couple close-up pictures if it can help to identify the flame sensor or other problems.

[Noon-Air]

what did your local tech tell you??

[gofish]

I can probably help you out but first post two more pictures: one of the pilot burning, the other of the opposite side of picture #2 ie a picture of the flame sensor & the pilot together....

[tysonjm]

Thanks, here are the pics based on what you described. See if they're sufficient...I'm just not sure what/where the flame sensor is supposed to be.

I'll stand by, and let me know if you need more info - thx!

snipped-for-privacy@g> On 14 Jan 2007 11:47:34 -0800, [e-mail] wrote: >

[tysonjm]

Another pic with a better angle:

snipped-for-privacy@g> On 14 Jan 2007 11:47:34 -0800, [e-mail] wrote: >

[gofish]

partner, you need serious help. Magic Chef should have stuck with what they do best, which is NOT building furnaces....

An early 80's model you say?

so if you have a pilot......AND you know how to apply 24v to the gas valve....you may get lucky & have heat temporarily. I'm betting the gas valve is toasted and no matter WHAT you do, you aint gonna have heat. now a sharp cookie could put you in a retrofit kit for $750, but hell, thats a down pymt on a brand new furnace....

I'm guessing you're in So Cal. what do you think of that bitter freeze we're getting?

[tysonjm]

Thanks for taking a look...I figured our Magic Chef furnace wasn't too promising when we bought this place 2 yrs. ago. You might be right on the gas valve since when I hear the repeated clicking, I'm seeing a spark emitting each time...it seems to get the pilot going, but I assume that spark is also supposed to get the burners rolling, but not enough gas?

Yeah, the SoCal chill...I guess we don't have it so bad considering other parts of the country, but it's enough to warrant turning on the heater you'd expect to work!

snipped-for-privacy@g>

[Oscar_Lives]

Nice....

[tysonjm]

Thanks for taking a look...I figured our Magic Chef furnace wasn't too promising when we bought this place 2 yrs. ago. You might be right on the gas valve since when I hear the repeated clicking, I'm seeing a spark emitting each time...it seems to get the pilot going, but I assume that spark is also supposed to get the burners rolling, but not enough gas?

Yeah, the SoCal chill...I guess we don't have it so bad considering other parts of the country, but it's enough to warrant turning on the heater you'd expect to work!

snipped-for-privacy@g>

[Anonymous]

Looks like a flame switch. I think you have a small white spark relight module, and a flame switch that plugs into the gas valve. You could have a bad flame switch or gas valve, or just a dirty pilot not hot enough to close the hot side of the flame switch.

Or your electrode might be the flame sensor, if wired to a module with mv, pv spark terminals..you could have a bad module or a dirty electrode/sensor.

-Canadian Heat

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[tysonjm]

[Power's Mechanical]

Its actually called a auto pilot. Readily available and made by White Rodgers. Its a mecury switch has to be properly disposed of. Not just tossed into the trash.

snip

[Anonymous]

Well if your pilot lights and the ticking stops, I'm assuming the auto relight is satisfied, and the gas valve is waiting for the flame switch to open.

The chances are greater the mercury flame switch is the problem rather then the gas valve. If the pilot is dirty and the little flame doesnt heat the flame switch up then the burner won't light. I usually remove the pilot orifice and try to clean that. Or just blow and suck on the pilot tubing while you hit the pilot hood with a wrench. Mercury switch is very easy to replace. Make sure not to unravel the capillary anymore then needed. And keep note of where the existing rod is sitting, inside the pilot assembly. You want it to sit just right inside the flame. Normally after the pilot lights it showed take no more then 120sec to open the gas valve. 30sec is what I am used to waiting.

-Canadian Heat

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[tysonjm]

Thanks. This sounds like it's worth a try at least before calling in someone. I did manage to take out that little assembly, but still just am not sure which part is which, i.e. pilot, pilot hood, flame switch, etc. Maybe this new pic will help? I've put letters on the different parts, but don't know what each is:

I tapped a couple things lightly and blew some compressed air to clean, but when I put it back the pilot won't even light anymore...I probably really messed something up now, but I figure the thing is so old it eventually needs replacing anyway. Let me know if you can help me identify the parts to do what you described. Thanks!

[e-mail] wrote:

[Bubba]

I believe someone from the Smithsonian called and is looking for that. Bubba

[Anonymous]

bubba's an idiot, he's the old dinosaur that should beat it.

Wow nice pic and labels hehehe

A= flame switch (follow the skinny copper capilary, it should plug into the gas valve.

D= electrode (sparker)

B= pilot hood

C= flame runner

So you don't hear a spark or clicking now? If it's not lighting the pilot tubing could be full of air from you cleaning it, just try a few times until the air purges out.

-Canadian Heat

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[tysonjm]

Hey, I stepped away from this project for a few days...Identifying the parts really helps for my knowledge (thx!), but nonetheless, I think it's dead. All I've got now is a clicking with a spark, and it'll just do that until I turn the thermostat off or unplug the furnace. Not sure why the pilot doesn'tlight anymore other than something getting tweaked when I removed that whole little assembly to attempt a quick cleaning. The tubing that seems to carry the gas feels a little looser now despite the nuts still feeling completely tight...what an odd thing, the way this is set up. Oh well, hopefully, I can get a kit or something without having to spend $1,000s on a whole new furnace. :O