Girlfriends Parents Coleman Furnace not working.

[Sandy]

When I was using the mirror I could see a bright white spark from the igniter up to the pilot area. I'm thinking the pilot orifice may be clogged as mentioned earlier. The way it is set up there is not way to light the pilot with a match. There is a guard in the way and getting to the pilot is kind of a pain as well with out removing the guard plate. I did smell gas though which might tell me that the gas is trying to get through the pilot orifice?

Pilots only put out as much as about like a bbq lighter maybe a bit more. You might be able to smell gas. Sometimes they use a piece of bent up wire with a match holder on the end to reach back in there. The spark is a good indicator that that part works. Ive got one with a small alligator clip on it too as well as a couple of other homemade do hickies.

[N2 Welding]

Ok so lets say I can get a long lighter for bbq's and hold the flame on the thermo-couple. That should in theory heat the T-couple enough to send the signal to the solenoid on the gas valve to open? Is there a test I can do with a voltage meter to see if the thermo couple is bad in the even the gas valve does not open with a simulated pilot light from a bbq lighter?

[Sandy]

One side note, if this is a typical pilot light, the gas knob has to be in the 'pilot' position to light it. Then once it is lit and stays on the knob gets turned to the 'ON' position.

[Sandy]

I'm not sure what slight voltage reading you get off the coupler. Pretty subtle. It's a wire inside an insulated tube, shorted at the very end.

[N2 Welding]

One side note, if this is a typical pilot light, the gas knob has to be in the 'pilot' position to light it. Then once it is lit and stays on the knob gets turned to the 'ON' position.

There is no pilot position on the on/off gas valve. It is either on or off. Not set up like a water heater.

[Sandy]

There is no pilot position on the on/off gas valve. It is either on or off. Not set up like a water heater.

Nothing that says push and hold? Then you've got an auto pilot system where where it ignites every time it calls for heat maybe. Not much help with those.

[ronsii]

Did this furnace have a wiring schematic attached to any of it's covers?

might come in handy for testing purposes...


right now from what you said it looks like could be a few different possibilities...

pilot orifice gunked up...

thermocouple not working...

gas valve pilot not working...

controller for auto ignite not sending pilot voltage...

could be more but I haven't done much with auto igniters...

[N2 Welding]

Nothing that says push and hold? Then you've got an auto pilot system where where it ignites every time it calls for heat maybe. Not much help with those.

Yes Auto Pilot. Sorry I said auto igniter for Auto Pilot.

The furnace is an older Coleman Model 8631C636 that is having an ignition problem. It has an auto igniter for the pilot flame that is just clicking for the most part and not lighting the pilot flame. Every once in a while after turning the gas off at the valve and the power switch then turning them back on I can get the pilot to ignite for a second or two then goes out and stays out.

[ronsii]

A simple test you could do is like you were thinking hold a match/barby lighter to the pilot and see if it lights when you turn it on... keep away from the zappers!!!

[N2 Welding]

Did this furnace have a wiring schematic attached to any of it's covers?

might come in handy for testing purposes...


right now from what you said it looks like could be a few different possibilities...

pilot orifice gunked up...

thermocouple not working...

gas valve pilot not working...

controller for auto ignite not sending pilot voltage...

could be more but I haven't done much with auto igniters...

There was a couple of different schematics. Two inside the furnace that were almost identical but different color labels and one and the back of the door. I should have taken a picture of those.

I am hoping the main burners will ignite with a bbq lighter on the pilot thermo couple. With the pilot not lighting my best guess would be a clogged pilot orifice or something in the gas valve not allowing gas to get to the thermal couple.

Edit: Sorry if I missed and did not answer any questions. This thread moved a lot faster than I imagined it would Thank you all for that

[N2 Welding]

A simple test you could do is like you were thinking hold a match/barby lighter to the pilot and see if it lights when you turn it on... keep away from the zappers!!!

Will do

[ronsii]

The pilot has to be lit and keeping the thermocouple hot or gas will shut off even if you get the main burners lit...

here is what you need to see... *if* you can get the pilot lit make sure some of the flame is hitting the thermocouple sensor end... if it doesn't then nothing else will work.
These are just generic pics but should give you the idea..

[ronsii]

Well, I gotta get up in 5, so good luck, be careful don't singe your eyebrows off!!!

[N2 Welding]

Got it, thanks guys I have a better idea what to look for now. I'll report back with what I find in the morning. Goodnight.

[Denis G]

Many possible causes for your problem, but don't forget to check the exhaust flue pressure switch:
http://www.hvachowto.com/2015/10/26/...essure-switch/
I've had this as a cause of failure before and it's an important safety check.

[T man]

FWIW,

my home's furnace has an auto ignite and thermocoupler as well. Every couple years, the furnace tries to kick on, but then immediately shuts off. It's an easy fix, for me anyways, and doesn't cost a dime.

I access the thermocoupler with a fine sandpaper, or steel wool. I clean it so it's "shiny" again. All the fuzzies from the summer land on it, and prevent the thermocoupler from reading getting the millivolt signal to the valve, and shuts it down. Once it's all clean, it starts up, and I'm good till the next episode, a year or two down the line.

Remove the shield, as other's have said, and clean the theromocoupler end so it's shiny and new looking. Try starting the unit.

While you're in there, vac out any big fuzzies you find.

[thegary]

I hate to burst any bubles but it looks to me like that furnace has electronic ignition . If so there is no pilot light. That is why his gas valve has no pilot position. Auto pilot is just another name for electronic ignition. I have just glanced at this and might be wrong but that is what it looks like to me. It is also looks to not be a high efficiency furnace so will not have an flue blower thus will not have a flue pressure switch as stated in post 40. If the ingnition is sparking then the igniter is working.

If he removes that cover above the burner I think he will see that there is no pilot light to light.

I have never seen a furnace that had an electric igniter to light a pilot light but if so it must be from an era from the time of transition from pilot light to electronic ignition. If so it must be from the 70's or early 80's

[T man]

You have the old version of the theromocoupler valve, which I'm sure can be purchased at the local HVAC supply, as long as it's not been discontinued.

The standard hardware store unit won't work in your situation, as you have a furnace that's older than my shorts.


lol

The universal one that's sold at hardware stores won't work in your situation, as it's not mounted to the gas valve in the newer format of just "screwing it in" as seen in the second pic.


That units so old, might want to either have it inspected for heat exchanger cracks, or simply replace it for a more efficient unit. You would save money in the long run, as the newer units are much more efficient. THey just won't last as long as that one did.

[thegary]

Thanks Tman , I was a little confused looking at it. I think it is from the 70's or early 80's . I would guess he will have a hard time finding a thermocouple for that but who knows .

Best he can do would be to remove it and take it to a hvac supplyhouse and see what happens.

[T man]

I hate to burst any bubles but it looks to me like that furnace has electronic ignition . If so there is no pilot light. That is why his gas valve has no pilot position. Auto pilot is just another name for electronic ignition. I have just glanced at this and might be wrong but that is what it looks like to me. It is also looks to not be a high efficiency furnace so will not have an flue blower thus will not have a flue pressure switch as stated in post 40. If the ingnition is sparking then the igniter is working.

If he removes that cover above the burner I think he will see that there is no pilot light to light.

I have never seen a furnace that had an electric igniter to light a pilot light but if so it must be from an era from the time of transition from pilot light to electronic ignition. If so it must be from the 80's

Yes, he said no pilot light, but it does have the thermocoupler which senses the flame is on, and keeps the solenoid on the valve open. By accessing that panel, he should be able to get to the TC and clean it.

here is mine, on my furnace.

IMO, that furnace inefficiency warrants replacement, but everyone's budget is different.

Hopefully he can simply clean it, and have it up and working again.

[thegary]

If I were to fix it I would probably install something like this. https://www.ebay.com/itm/HONEYWELL-Y...ESJQ:rk:3:pf:0

[ronsii]

You have the old version of the theromocoupler valve, which I'm sure can be purchased at the local HVAC supply, as long as it's not been discontinued.

The standard hardware store unit won't work in your situation, as you have a furnace that's older than my shorts.


lol

The universal one that's sold at hardware stores won't work in your situation, as it's not mounted to the gas valve in the newer format of just "screwing it in" as seen in the second pic.


That units so old, might want to either have it inspected for heat exchanger cracks, or simply replace it for a more efficient unit. You would save money in the long run, as the newer units are much more efficient. THey just won't last as long as that one did.

Great info T-man.... where were you last night? when we were stumbling around in the dark.

[T man]

Great info T-man.... where were you last night? when we were stumbling around in the dark.

Hell, I was out repeating things said by other people already in my neighborhood. If I'm gonna be an arse online, might as well be one at home too!

[N2 Welding]

Ok I was able to get the unit to light the pilot a couple of times but nothing would happen beyond that. I even put a propane torch from a distance pointed at the thermal couple and still nothing.

T-MAN is correct money is tight for them at the moment. Single family income trucker who's income is short after the old company sold out to a different name. Gorden truck lines is the company that sold out. Anyway I am trying to help them avoid a very costly repair.

[ronsii]

sounds like thermocouple is bad or something downstream from it.


EDIT: unless there is another safety interlock preventing startup like was mentioned earlier... flue pressure switch... etc...