Atwood Furnace Ignites But Won't Stay On

[2ndwindranch]

Was reading other posts in this forum, trying to identify a similar issue we are having.

We recently got a used cab-over camper, a 2002 Summerwind 805 that was hardly ever used.

The heater, to our knowledge, has never been used.

After cleaning it out to find a LOT of unwelcome creatures such as wasps, wasp nests, mud, and a DEAD BAT, here's where we're at:

Turn on fan switch
Turn on Thermostat
Move temp to hot
About 30 sec, hear fan come on
About 15 to 30 sec hear ignition clicks
and hear ignition, and the sound of a healthy furnace
That running lasts about 5 seconds, then the burn sounds stops
15 seconds later, ignition clicks and immediately ignition and burn sounds again

That cycle repeats constantly until we turn it off. The first time we had this cycle happening, we had horrible smoke coming out the exhaust, so something was definitely lighting and getting hot (for 5 sec). We immediately shut it off and cleaned even more, but we can't find what else to take apart and clean? Or, other thoughts?

Any help is greatly appreciated!
Thanks!
Tracey

[Byron Kinnaman]

If it was me with that problem I'd look up the manufacturer and find a local certified repair shop for brand and model. Take the whole camper to them and pay them to fix it. You camper and your truck are worth a lot more than could be saved by attempting to do the repairs yourself and not do a complete job.

I don't know about you or others reading this but I don't like loud booms.

[2ndwindranch]

Ya, but, my husband is a pretty handy guy, that will be the last resort. There are people with similar issues, but haven't found one in this particular order.

[gordon2]

No mention of the model of the Atwood, so lets try this...

http://bryantrv.com/docs2/docs/hflamefurn04.pdf

PS, I have to agree that some trained service tech help is appropriate. A ten year old camper, hardly used and obviously not maintained (from your description)....

In addition to trouble shooting the furnace, the propane system needs a full check up for one thing. Try to avoid this:

http://www.fiberglassrv.com/forums/f...eak-85379.html

by doing this:

The RV Doctor: What the Pro's Do - Propane System

[Komrade]

Sounds like some safety that shuts it down bc it does not detect heat and wants to protect from gas spreading. Research sensors on the unit. Disclaimer: I know almost nothing about furnaces and never fixed one, but had similar experience with home gas fireplace.

[2ndwindranch]

Originally Posted by Komrade

Research sensors on the unit.

That's a good point, we'll spend some time on this today then.

[QUOTE=Komrade;725042]Disclaimer: I know almost nothing about furnaces and never fixed one.../QUOTE]
Love it, thank you!

[2ndwindranch]

Originally Posted by gordon2

No mention of the model of the Atwood

Totally forgot to mention model and meant too... it's an Atwood 7912-II and we downloaded the manual for that as well.

It's the same model I saw on another thread with a similar issue, but their sequence of events of error is slightly different and didn't want to confuse the thread with our issue.

I appreciate all the heads up and words of caution.

[threepine]

I would check the air intake pipe to make sure there are no holes or blockage and it is securely fitted. On our Atwood this was about a 4" diameter flexible hose.

[2ndwindranch]

Originally Posted by threepine

I would check the air intake pipe to make sure there are no holes or blockage and it is securely fitted. On our Atwood this was about a 4" diameter flexible hose.

Will double-check that too, but I think we've done all of the hose clearings. We had our shop vac on every piece (with the entire heater disassembled) vacuuming from each end of any and all tubes and put our hand on each side to feel the suction of the vacuum.

We have to keep referencing the manual for what part is what, but something we're thinking but can't identify is the 'air return'? We see it mentioned a lot in the manual, but see nothing called that in the furnace diagram.

But, air flow, and sensors seem to be our number one possibility, because we are getting a flame and a 5 seconds of run time, then auto shut off, so both seem like offending sources.

[ZachO]

I'd say if you cleaned it once and something was still left to burn, then maybe one more dissasembly and cleaning couldn't hurt, just to make sure. Kinda sounds like something is overheating and causing it shut down for safety.

If you were reading my Atwood furnace post, I think there's a link (or at least mention) of a rebuild kit of some sort available online. It includes replacements for all the typical parts which fail over time. Assuming everything is actually cleaned out and clear, there's not much more to the thing except the gas ports and electronics. Other issues could be corrosion and rust holes.

[2ndwindranch]

Originally Posted by ZachO

If you were reading my Atwood furnace post, I think there's a link (or at least mention) of a rebuilt kit of some sort available online.

Yes, I believe it was yours! I'll go back and find that. We've gotten really good and pulling the furnace out, stripping it down to nothing and putting it back together again, so it could very well be that. Worth a shot vs. spending almost $800 on a new one, thanks for the input!

[ZachO]

Yeah honestly if my trailer had come with a Suburban heater, I'd have probably just replaced it. But I like the Atwood, and it's a different shape and exhaust setup than Suburban, so switching one for the other doesn't work without modifications to cabinets and the trailer shell. But since the Atwood is so expensive, fixing it is definitely worth a try, assuming it's not corroded/rusted.

I finally put quick-disconnect wire connections on my furnace wires, after cutting and crimping "permanent" wire connectors on there 3 times. I got pretty good at getting mine in and out after a little while too.

My suggestions (and other people's suggestion) is, if you haven't already, to read the manual well. It gives a fairly clear "order of operations" letting you know what's happening at each step along the way to a successful ignition and cycle. Understanding that process makes trouble shooting the cause a lot easier.

At some point if things don't make sense, it can often be a circuit board problem. That was definitely the underlying issue with mine. At least it was the underlying issue until I blew the fuse and didn't realize it...

[2ndwindranch]

Originally Posted by ZachO

assuming it's not corroded/rusted.

It's very clean and not rusted or corroded, just a lot of happy varmets finding refuge, so once all that stuff is out, it looks brand new. I like it too, the ignition sequence lights up like a champ so I feel like once we get this fixed, it will be great and I won't freeze all weekend like I did Friday night!!! That sucked!

[Gerry]

Originally Posted by threepine

I would check the air intake pipe to make sure there are no holes or blockage and it is securely fitted. On our Atwood this was about a 4" diameter flexible hose.

I agree with Rick.
My newly bought was doing the same thing but would run for about 5 minutes and I found that the air intake was not a tight fit onto the furnace intake pipe. I filled this 1/4 space between inner and outer pipe with fireproof gasket material that I got at a woodstove shop and it cured the problem.
The wind was actually blowing out the flame but when I filled thus gap flame was nice and steady.

[Kenny Strong]

I have this Atwood in my 13' " Lil Bigfoot ". If the side access to the fan is removed and the exhaust pipe is pulled out the side air could be blown IN with a powerful leaf blower.or a high pressure air hose with the exhaust opening blocked to keep air in pipe it could blow the possible paper wasp nest out from the flame area. there is no reason for smoke to be coming from anywhere else. there are no burnable parts here, or near here.metal parts will not produce smoke. they could heat up and cause serious over heated metal odors, but not smoke. The parts are kept cool by the fan, for the 5 seconds it is on. the fan cools these parts to heat the interior.( radiator)
Does air exit the exhaust pipe, when the fan comes on?

[cpaharley2008]

and once you get it running, install a varmint cover over the exterior exhaust vent.

[GonHuntin]

The thermocouple is bad.

Kindergarten explanation....When the ignitor lights the pilot, it heats the thermocouple which generates a small electric current.....the current tells the control board to open the gas valve......the gas valve stays open until the thermostat tells the control board that the set temp has been reached.

When the thermocouple goes bad, the ignitor lights the pilot and the gas valve may briefly open allowing the burners to light......however, when the control board does not see the electrical current from the thermocouple, it closes the gas valve.

[Kenny Strong]

John I think ya got it

[Kenny Strong]

I meant Mark's answer sounds so correct. What about the smoke ?

[wilyoung]

Originally Posted by Kenny Strong

I meant Mark's answer sounds so correct. What about the smoke ?

There must have been something left in the burner chamber (paper wasp nest, dead creature, whatever) that burned on first lighting. Wouldn't hurt to open it up as much as possible and check again for residue.


I was about to add the last step in the ignition series - There is either a thermocouple or ionization detector in the flame area that detects that the flame is burning. If it doesn't detect the flame within a few seconds the furnace shuts down again. If the burner definitely lights that sounds like what is happening. It may wait a few seconds and try again. This may repeat a few times, then shut down permanently.



Burning extraneous material might effect an ionization detector. It could be a bad thermocouple/detector, disconnected or broken wire, or circuit board problem. That's where I'd look next.