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 > Atwood Hydroflame Furnace Issue

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Old Islander

British Columbia

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Posted: 12/04/17 02:30pm Link  |  Quote  |  Print  |  Notify Moderator

Our 2005 Okanagan Truck Camper has an Atwood forced air furnace. When it comes on, it works well -- warms the camper up quickly. The problem is, it will only come on if the furnace itself is cold.

At first, I thought it was the wall mounted thermostat. So removed it, and experimented by turning on the cold furnace by clipping the two wires together (the ones that attach to the back of the thermostat) -- thus closing the circuit. The furnace came on normally, and I let it run for about 5 minutes; then unclipped the thermostat wires, opening the circuit, and the furnace shut down normally.

Then about 20 minutes later, tried clipping the thermostat wires together again, and the furnace would not come on -- no reaction whatsoever -- no fan, no clicking -- nothing. It was over an hour, before it would once again start up, suggesting an issue with the furnace's internal temperature?

There must be an adjustment for this -- an internal thermostat of some kind (that prevents a too-hot furnace from running)?

It'll likely have to be fixed by an RV shop, but I'd like to know a bit about it, so I can explain to the tech exactly what the problem is.

Any advice will be greatly appreciated...

Thanks
Steve

BFL13

Victoria, BC

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Posted: 12/04/17 03:09pm Link  |  Quote  |  Print  |  Notify Moderator

Might be something here:

http://www.atwoodmobile.com/manuals/furnaces/MPD%2033179%20SP%201.08.pdf


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YC 1

Yuba City Calif./ Auburndale Florida

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Posted: 12/04/17 04:14pm Link  |  Quote  |  Print  |  Notify Moderator

There is internal safety devices. If the thing is overheating it may keep it off.


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Old Islander

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Posted: 12/04/17 04:33pm Link  |  Quote  |  Print  |  Notify Moderator



Thanks for this -- it's better than the one that came with the camper. Will spend some time going thru it and see if anything comes to mind...

Old Islander

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Posted: 12/04/17 04:44pm Link  |  Quote  |  Print  |  Notify Moderator

YC 1 wrote:

There is internal safety devices. If the thing is overheating it may keep it off.


I don't think it's overheating, but maybe the furnace "thinks" it is...?

This was happening on a recent trip where it was below freezing for much of the time we were there. So will have to figure out what component of the furnace will prevent it starting up, if it "thinks" it's overheated. Circuit board? Relay switch?

Another possibility -- I see that the ignition system has a safe-guard that shuts the furnace down for an hour, if after 3 tries, the flame fails to light. That's about the amount of time it takes for the furnace to light up again, after the desired temperature inside the camper is reached, and the furnace shuts down.

newman fulltimer

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Posted: 12/04/17 05:23pm Link  |  Quote  |  Print  |  Notify Moderator

or your regulator is allowing to much pressure the unit heats up to fast snaps the overtemp switch open then cools down switch closes and it restarts

Old Islander

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Posted: 03/12/18 05:28pm Link  |  Quote  |  Print  |  Notify Moderator

Well, three months later, and I am pleased to report that the problem is solved. It was the limit switch. This switch is mounted in the plenum and if the furnace gets too hot, it shuts the fuel valve off, effectively killing the flame, but permitting the fan to continue running. The switch in mine was too sensitive, shutting down the furnace during normal operating temps.

I found a post somewhere at another site, suggesting the limit switch might be the problem. I contacted a local RV repair shop and they agreed. Their quote was between 3 and 3.5 hours (at $98 per hour) to remove and re-install the furnace, and replace the switch. Parts would be $100 to $125.

I found the switch online (Amazon.ca) for approx. $25 including delivery. I bought a new sail switch too, simply because it was going to be exposed, so why not? I didn't have to remove the furnace -- just the circuit board, squirrel cage, and cover. Didn't even have to remove the fan motor -- the limit switch is just behind it. Put it all back together and the furnace works perfectly now.

So I'm quite delighted...! A $450 to $500 repair for about $55.

BFL13

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Posted: 03/12/18 06:11pm Link  |  Quote  |  Print  |  Notify Moderator

Well done! (BZ)

trailrider

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Posted: 03/12/18 10:18pm Link  |  Quote  |  Print  |  Notify Moderator

Wow, crooked shop to quote you that price!


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Old Islander

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Posted: 03/13/18 12:03pm Link  |  Quote  |  Print  |  Notify Moderator

trailrider wrote:

Wow, crooked shop to quote you that price!


Yeah, I wondered about that, too. I guess I'll give them the benefit of the doubt -- maybe they would have figured out that the furnace didn't have to be removed when they actually saw it. Their quote was 'sight unseen' over the phone...

But after this, I'll likely not take the camper to them for any other issues that crop up...

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