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Open Roads Forum  >  Tech Issues

 > Furnace runs but blows cold

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Teleman

Clayton, CA, USA

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Posted: 02/05/21 07:59pm Link  |  Quote  |  Print  |  Notify Moderator

Part way through our two week trip our furnace stopped working. It's an Atwood Hydro Flame 8500-IV, in a 2000 Airstream Land Yacht. Does anyone have experience with these furnaces and if so can you suggest how I might proceed to troubleshoot this problem? It would be great if just replacing the board solved the problem as its readily accessible. I think the igniter and sail switch might be difficult to access. Any helpful info would be greatly appreciated.

RobWNY

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Posted: 02/05/21 10:56pm Link  |  Quote  |  Print  |  Notify Moderator

80% of the time, it's the sail switch


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Bionic Man

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Posted: 02/05/21 11:00pm Link  |  Quote  |  Print  |  Notify Moderator

Propane full?

Do you have a propane leak detector that is past its expiration date?


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Teleman

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Posted: 02/05/21 11:27pm Link  |  Quote  |  Print  |  Notify Moderator

Bionic Man wrote:

Propane full?

Do you have a propane leak detector that is past its expiration date?

All the other appliances work...stove, fridge, hot water heater. I don't think it's a propane issue as it just stopped igniting. I don't hear the igniter either.

Teleman

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Posted: 02/05/21 11:28pm Link  |  Quote  |  Print  |  Notify Moderator

RobWNY wrote:

80% of the time, it's the sail switch

I was afraid of that. Are you familiar with this unit and what is involved in replacing it?

enblethen

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Posted: 02/06/21 06:48am Link  |  Quote  |  Print  |  Notify Moderator

Sail switches are effected by low voltage to motor not allowing in to come up to full speed. Many times sail switches contacts are not closing due to a very small piece of debris. Can quit often be blown out by compressed air.


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Dutch_12078

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Posted: 02/06/21 07:24am Link  |  Quote  |  Print  |  Notify Moderator

The first thing I typically do for an RV furnace or water heater failure to ignite is disconnect and reconnect the wiring and ignition/sensor connectors a few times at the ignitor board to see if the problem is as simple as some contact corrosion. The ignitor/sensor connection in particular can be a problem since the sensor mode is working with millivolts. If that solves the problem, then I suggest using an appropriate contact cleaner at the first opportunity. I've worked on at least 100+ RV furnace problems over the years, and only replaced a couple of sail switches. The rest with ignition problems have generally been failed igniter boards, mis-adjusted or cracked igniters, failed gas valves, etc. Reseating the connectors alone has worked a surprising number of times.

Maybe Doug Rainer will stop in and lend his professional expertise to the problem...


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ksg5000

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Posted: 02/06/21 12:25pm Link  |  Quote  |  Print  |  Notify Moderator

Low battery is a common reason for furnaces not firing up - when a battery is low it won't run the furnace fan at high enough speed to open the sail switch. If battery is Ok then check the sail switch.


Kevin

Teleman

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Posted: 02/06/21 12:43pm Link  |  Quote  |  Print  |  Notify Moderator

Thanks for all the info. Low battery isn't the issue as they were fully charged. I'll see if I can get compressed air to the sail switch. I did try unplugging and re plugging the contacts on the board terminals. I'll try some contact cleaner too.

enblethen

Moses Lake, WA

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Posted: 02/06/21 01:34pm Link  |  Quote  |  Print  |  Notify Moderator

Can of air with the tube works pretty good!

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