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Topic: Atwood 8516-III and 8535-III Furnace high temp limit switches (Read 1290 times) previous topic - next topic

Atwood 8516-III and 8535-III Furnace high temp limit switches

Still working my way thru these OEM 25 year old furnaces.  What is the location of the high temp limit switch and what do I have to remove in order to access or replace ?
Jon Harris
1995 U300 Unihome
Cat 3176
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Re: Atwood 8516-III and 8535-III Furnace high temp limit switches

Reply #1 –
Quote from: Jon H –
Still working my way thru these OEM 25 year old furnaces.  What is the location of the high temp limit switch and what do I have to remove in order to access or replace ?
can't help you yet but just now trying to find the parts for my 8516-111
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: Atwood 8516-III and 8535-III Furnace high temp limit switches

Reply #2 –
Jon,

It looks like you will have to pull most of the unit out to get to that switch.  Here is a page of diagrams and repair kits for the Atwood models. Atwood - HydroFlame Furnace Tune-Up Kits | pdxrvwholesale

Here's a couple of troubleshooting videos on the Atwood furnaces.  The 8535 IV  he is working on has a on/off switch that ours doesn't have.  The 8535 III I believe only has a reset button on the motor.  You should be able to test that high limit switch first before pulling it out if that's your problem. 

In the second video you'll see where the high temp limit switch is located. 

Sharp young man and excellent instructional videos to help you test the components before replacing them.

Jerry

https://www.youtube.com/watch?v=DSdxeaRzRx0

https://www.youtube.com/watch?v=E05pEyYpXTI
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Jerry and Cindy Maddux
1993 U300/36WTBI DD6v92TA
build 4271  "Miss Lou"
1995 suzuki sidekick 4x4 toad
Gulfport, Ms

"Pride of Ownership"
 

Re: Atwood 8516-III and 8535-III Furnace high temp limit switches

Reply #3 –
My front furnace (Atwood Hydro-Flame 8535-II) was still working good but noticed that funky burned, not raw gas smell inside the coach.  It wasn't enough to set off the Safe-T-Alert which would trigger the shut-off solenoid on the main tank, but was easily detected with my hand held Home-Flex flammable gas leak detector.The Home Depot Logo It's a very handy little device to have when working around gas to check for small leaks that you may not be able to smell.  This let me know that the gas valve was leaking because the smell went away and the Home-Flex didn't trigger when the main tank was turned off. 

I had changed the burner out already which is obsolete about 10 years ago but was still good.  The original gas valve #31155 was also obsolete but I was able to find a replacement gas valve Dometic #31098 which would work  Robot or human?

I was able to use the existing mounting bracket by bending it downward to give clearance for the igniter connections. The gas inlet is on the side and will line up to the existing gas connection using the old fittings.

I transferred the manifold from the old valve to the new one and replaced the igniter #36999, Gasket #32172, and orifice #31080.  These can be found on Ebay, Walmart, or Amazon.   

I had to turn the black plastic seal for the gas line on the cabinet straight up to make it fit and cut some aluminum sheet from Home Depot to cover the gaps created.  I used yellow teflon gas tape and checked for leaks at the connections.

The furnace works like new with no leaks and no smell.  Cost about $125 to fix it and I don't have to replace it for now. 

Jerry
The selected media item is not currently available.
Jerry and Cindy Maddux
1993 U300/36WTBI DD6v92TA
build 4271  "Miss Lou"
1995 suzuki sidekick 4x4 toad
Gulfport, Ms

"Pride of Ownership"