Coleman Mobile Home furnace Help!!!

Questions about repairs and parts for Coleman furnaces, air conditioners and heat pumps for manufactured homes. Click here for Coleman parts.

Moderators: Greg, Mark

Locked
Sokniw
Posts: 6
Joined: Mon Oct 08, 2012 4:09 pm

Mon Oct 08, 2012 4:21 pm

I have a coleman forced air 7975C656 model furnace with a electronic ignition, its a gas furnace.

Here is what happens.

I go to turn the furnace on, the induction motor kicks on and than a few seconds after that the flame ignites, i watch it through the view window it seems to be a decent size flame, it starts off small than gets bigger within seconds, than about 5-10 seconds after than i can see some sparks in there, like its trying to ignite itself again and the flame goes out. i have had this running off and on for the past few weeks. if i leave it on it will keep igniting and going out over and over.

I have cleaned the flame sensor rod, it wasn't dirty at all and the porcelain is not cracked at all, i showed it to a hvac guy and he said it doesn't look bad. on my furnace the electrode has the flame sensor attached to it its all 1 unit, so i cant just replace the flame sensor but the hvac guy said he would steer in another direction cause those dont fail to often.

I dont want to pay for a service call cause we just moved in here, and have exhausted all our resources fixing up the place. The guy i talked to said its probably my ignition module box.. i dunno im at a loss.

But a recap, i turn the furnace on it all turns on like it should flame ignites after a few seconds you can hear and see it sparking like its trying to ignite again and bam it turns off, and this will keep doing it over and over and over, like if i just kept the furnace on, it would keep doing it over and over non stop. So the furnace does not shut completely off just the flame goes out.


DaleM
Posts: 385
Joined: Wed Apr 07, 2010 10:07 am

Mon Oct 08, 2012 8:47 pm

Can you pull the burner assembly and post a picture of it? I have a few ideas but need to see that burner assembly first before I make any recommendations as to a repair.

Sokniw
Posts: 6
Joined: Mon Oct 08, 2012 4:09 pm

Mon Oct 08, 2012 9:02 pm

DaleM wrote:Can you pull the burner assembly and post a picture of it? I have a few ideas but need to see that burner assembly first before I make any recommendations as to a repair.
What were you thinking im at work right now, but im open to suggestions, i was just about to order a new electrode and ignition module, now your making want to wait but its getting cold here in minnesota.
Ill take a picture and send it but if you had a suggestion i could try at the time i take it apart im open to it, the mounting plate's on the electrodes are really rusted not sure if that matters or its used as a ground of some sort at all for current.

What ive done so far,
- Ive cleaned the electrode wire's off with some steel wool and emery cloth
- Re did the wire connections for the ignition cause before it was barely holding on by a wire.
- i couldnt get the valve nozzle off to clean behind it but i have seen suggestions to clean it out with a que tip. i have also cleaned the valves nozzle off cause its kinda rusted.
- the furnace looks cleaned and the electrode looks clean.


and on another note, i had to change out the roof vent because the one that was on there the cap was rusted off so a gust of wind would blow it off, so i just a plain old cylnder vent thats about a 10" tall, with fins all the way around it. Not sure if that could have messed something up.

DaleM
Posts: 385
Joined: Wed Apr 07, 2010 10:07 am

Mon Oct 08, 2012 9:11 pm

That rusted roof jack from before could be your problem STILL!! I see rust falling onto the top baffle of the heat exchanger all the time. It blocks the flue gases from being able to exit the chamber and there isn't enough oxygen being brought in to support the flame.

Another thought I have is what all did you attach the new termination cap to? There are 2 pipes to that flue assembly. They both have to be clear to work properly. Fresh air for combustion goes in the outer pipe and exhaust gases go out the inner pipe. If you blocked either of them, and the WRONG roof cap will do that, the balance of air flow through your furnace will be disrupted and it will not function correctly.

Sokniw
Posts: 6
Joined: Mon Oct 08, 2012 4:09 pm

Mon Oct 08, 2012 9:17 pm

the old cap that was on there was rusted, but the vent pipe going down to the furnace was clean, i just pulled the cap/vent off that was rusted and slid what i have on there now. and the vent pipe that is coming out of the top of the furnace.

But i did pull that vent pipe all the way out it was like a 3feet section of pipe. i could see the top fo the furnace looked like a dampner or something was there. it looked really rusted. but it was so far down i dont think i could reach it.

Before it was just a open hole in my roof cause the hood of the cap that was on there before was rusted off and anything could drop down into the furnace. now it at least has a hood so nothing can drop down. and it was working fine with just a open hole i didnt think this would cause any problems.

But also i had it running for a day and than it decided to stop, than i had it running again and than it stopped doing the symptoms i posted above, i could get it working for a day than it stopped. now i cant get it going again..

But the flame gets pretty big it fans out pretty good, it isnt a small flame that just goes out thats what doesnt make sense to me, how big does the flame need to be.


DaleM
Posts: 385
Joined: Wed Apr 07, 2010 10:07 am

Tue Oct 09, 2012 7:26 am

That flame going out in full burn is an indication of not enough oxygen for proper combustion. Can you post a pick of the roof vent now that it has been changed? I suspect an air flow problem either from the new roof cap configuration or rust inside on top of that upper damper. Only way to get to that is either slide the 2 pipes up off the furnace from inside the home and clean it out with a shop vac. OR get several shop vac wands taped together to be able to reach down to the top of the unit inside the smaller pipe while on the roof. The latter is my preferred method since most innner flue pipes are rusted to the heat exchanger and won't come off easily.

Sokniw
Posts: 6
Joined: Mon Oct 08, 2012 4:09 pm

Tue Oct 09, 2012 8:52 am

The flame doesn't just poof go out I see sparks on the ignitor going like its trying to light itself and clock goes out

DaleM
Posts: 385
Joined: Wed Apr 07, 2010 10:07 am

Wed Oct 10, 2012 12:07 am

Does your furnace have a spark igniter or an HSI (hot surface ignition) igniter? Does your furnace have a pilot light with an Autopilot feature?

Sokniw
Posts: 6
Joined: Mon Oct 08, 2012 4:09 pm

Wed Oct 10, 2012 1:51 am

Spark ignitor

DaleM
Posts: 385
Joined: Wed Apr 07, 2010 10:07 am

Wed Oct 10, 2012 11:01 am

Then start with the obvious. You stated you pulled the inner pipe all the way out, did you put it back in? You changed the roof cap and THEN started having problems. Your actions with the roof jack assembly have caused what is happening. Clean out the baffle on top of the furnace with a shop vac. Be sure both sections of the roof jack pipes are in place and properly installed and get the right termination cap for your furnace/roof jack assembly. These are matched components and to get the most efficient use out of your furnace they should all be in place.

The reason the spark ignitor is working is because the flame sensor has detected a weak flame and the spark igniter is tryiong to relight it. It will not fire or if it does it will not run long. You need 3 things for fire and one of them is oxygen, it's not there.

Sokniw
Posts: 6
Joined: Mon Oct 08, 2012 4:09 pm

Mon Oct 15, 2012 6:17 pm

OK so i got it working, i put in a new electrode, and i also cleaned out the dampener on the roof with a shop vac, also installed a new t-stat that doesn't have mercury in it, it actually runs a long flame cycle and doesn't kick off every 4 mins.

But the problem i have now is my fan doesn't kick on, i bought a new switch thinking it was just that little switch, but i replaced it and connected the wires back on and it just heats up and after a while it just turns off as a safety feature i know it has. So what else could be preventing the fan from kicking on when it should, Right now i just have the 2 wires crossed together so its on all the time.

DaleM
Posts: 385
Joined: Wed Apr 07, 2010 10:07 am

Mon Oct 15, 2012 11:03 pm

Does the new fan switch have the same temperature rating as the old one? Example imprinted on the metal frame of the switch you will find numbers like: F115-20. If your new fan switch has a high rating it may not turn the fan on before the limit switch cuts the furnace off.

Locked