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Old 03-21-2023, 08:15 AM   #1
Hellbilly13
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Atwood Furnace Burning Plastic Smell

Atwood AFMD35131


I woke up this morning cold with the furnace fuse blown. Put a new 15A fuse in and as soon as the blower started the fuse blew. Took the cover off on the outside and checked the fan was free (it was), cleaned the sail switch (it had a lot of dust on it). Put that back together and put in a new fuse; it blew immediately after the fan started.


I read some other posts about similar problems and decided to throw in a 20A fuse just to see if it would run. It did, but had a bad burning electronics smell coming from the registers. I shut everything down and took the control board out and inspected (no obvious burnt components), pulled the igniter and cleaned with a wire brush, and inspected all wires and components I could see. Also cleaned the inlet filter (it was a little dusty). I put everything back together and installed a 15A fuse.



Now the furnace seems to be working just fine (it does not blow the 15A fuse anymore), but the burning smell is still there. I'm thinking its just blowing out smell from something that burnt earlier? I've worked on electronics for decades and know that smell lasts for a long time.



I'm not sure I'll be able to sleep until I can get some reassurance that this won't catch fire in the night. Does anyone have any other things I can check? I did not pull the blower unit out, but that seemed like a lot of work?
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Old 03-21-2023, 08:21 AM   #2
Kirk's Keystone Outback.
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Originally Posted by Hellbilly13 View Post
Atwood AFMD35131


I woke up this morning cold with the furnace fuse blown. Put a new 15A fuse in and as soon as the blower started the fuse blew. Took the cover off on the outside and checked the fan was free (it was), cleaned the sail switch (it had a lot of dust on it). Put that back together and put in a new fuse; it blew immediately after the fan started.


I read some other posts about similar problems and decided to throw in a 20A fuse just to see if it would run. It did, but had a bad burning electronics smell coming from the registers. I shut everything down and took the control board out and inspected (no obvious burnt components), pulled the igniter and cleaned with a wire brush, and inspected all wires and components I could see. Also cleaned the inlet filter (it was a little dusty). I put everything back together and installed a 15A fuse.



Now the furnace seems to be working just fine (it does not blow the 15A fuse anymore), but the burning smell is still there. I'm thinking its just blowing out smell from something that burnt earlier? I've worked on electronics for decades and know that smell lasts for a long time.



I'm not sure I'll be able to sleep until I can get some reassurance that this won't catch fire in the night. Does anyone have any other things I can check? I did not pull the blower unit out, but that seemed like a lot of work?
I had a recall on my 2018 TT, related to wiring being touching of the exhaust.
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Old 03-21-2023, 08:24 AM   #3
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I gained access to my furnace and repositioned the wires and secured them away from the exhaust. I haven't used my furnace prior to finding out by chance about this issue, but after seeing it, my wires would've smoked too.
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Old 03-21-2023, 09:14 AM   #4
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I had a recall on my 2018 TT, related to wiring being touching of the exhaust.
Thanks for the reply. I'm pretty sure that isn't the issue? I inspected all the wires in that area and didn't see anything amiss. I never received that recall for some reason (I've received others); my trailer is in that serial number range though. I've been full-timing in this rig for 3 years now and haven't had any issues with the furnace before today. We did move yesterday, so it's possible that something moved into a position to get burnt. It's just not where I can see it.
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Old 03-21-2023, 09:18 AM   #5
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I would remove the furnace and do a detailed inspection.

Added: RV furnaces DO NOT have an intake filter.
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Old 03-21-2023, 10:54 AM   #6
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Burning plastic smell is a big red warning. If you fail to heed that warning and proceed without knowing EXACTLY what caused it, you are putting everything including your life at risk. Nothing you described in your troubleshooting efforts is likely the cause. Something else is going on and you need to find out what it is.

I investigated a total loss house fire this past summer where lightning struck the house 3 days prior. He was advised to get an electrician to inspect his electrical system. The homeowner said everything was working normally so he didn’t bother calling anyone despite his wife telling him about the funny smell every time she was in one of the upstairs bedrooms and the light was on. Fortunately it burned down during they day when no one was home, but they lost everything including their pets.
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Old 03-21-2023, 12:04 PM   #7
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I would remove the furnace and do a detailed inspection.

Added: RV furnaces DO NOT have an intake filter.

So I'm guessing I should remove the filter that apparently was installed at the factory? It is a black mesh filter that is wrapped around the outside of the furnace. No one else has that?



I removed the furnace this morning and inspected everything I could see without completely disassembling the unit. Do you have any specific items in mind that I should inspect?


Thank you for taking the time to help.
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Old 03-21-2023, 12:06 PM   #8
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Originally Posted by NH_Bulldog View Post
Burning plastic smell is a big red warning. If you fail to heed that warning and proceed without knowing EXACTLY what caused it, you are putting everything including your life at risk. Nothing you described in your troubleshooting efforts is likely the cause. Something else is going on and you need to find out what it is.

I investigated a total loss house fire this past summer where lightning struck the house 3 days prior. He was advised to get an electrician to inspect his electrical system. The homeowner said everything was working normally so he didn’t bother calling anyone despite his wife telling him about the funny smell every time she was in one of the upstairs bedrooms and the light was on. Fortunately it burned down during they day when no one was home, but they lost everything including their pets.

That's exactly what I'm worried about! I just don't know what to do at this point except buy a new furnace. I'm hoping this one can be repaired, but I don't know where to look. I'm going to go remove it again and look for anything burned.
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Old 03-21-2023, 02:44 PM   #9
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I removed the furnace and took everything i could apart. Everything looks good, so I started smelling everything and I get a slight burnt smell from the motor. I'm going to go ahead and order one I guess. I won't be able to rest at night until I fix something.
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Old 03-21-2023, 04:13 PM   #10
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I know the situation is distressing and one I wouldn't trust to fate. Since you've ran into burned electrical components you know the smell and as you said it can be very strong and attach itself to things local to the problem. I've used my nose on many occasions to run down an issue like that (DW says I have a nose like a bloodhound).

You sound like me; I would not be using something that smoked then started working for a bit. It heated up enough to burn, you don't know what it is, what caused it or when it might happen again. If it cannot be verified 100% I would be replacing it. Not the best or cheapest option but I don't like burning surprises in the middle of the night. Good luck.
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Old 03-21-2023, 04:16 PM   #11
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If the motor smells, that might explain a few things. There could be a bad winding or the motor brushes could be worn. If that’s the case, and the fan stopped on a bad spot, it would just sit there and hum causing it to get really hot and eventually blowing a fuse. When you were cleaning and spun the fan blade it got it off that bad spot and works again for now. If it were me, I would be replacing the motor, or the whole unit and it sounds like you are on that track already. Best wishes and good luck with it!
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Old 03-21-2023, 05:24 PM   #12
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We lost our last camper to a hot water heater fire, we were camping with a group of friends in neighboring campsites and were about to leave for dinner. We put the fire out quickly and it also consumed the back of the refrigerator and burned through the roof in a very short time. We all worked in public safety and unplugged the camper, shut off the gas and used a hose to extinguish and then stayed on fire watch.

My thoughts are that something electrical failed and putting a bigger fuse defeated the protections that are built into the furnace for the size of the wiring. We used to do that with old screw in house fuses and thats the very reason those boxes are not allowed in new construction. It would be good to disassemble to investigate the inside to determine the cause and condition, a blower motor could be the cause and would be much cheaper if no wiring is compromised. This is also that point where I would pull it and take it to a technician for an informed opinion.
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Old 03-23-2023, 10:01 AM   #13
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I know the situation is distressing and one I wouldn't trust to fate. Since you've ran into burned electrical components you know the smell and as you said it can be very strong and attach itself to things local to the problem. I've used my nose on many occasions to run down an issue like that (DW says I have a nose like a bloodhound).

You sound like me; I would not be using something that smoked then started working for a bit. It heated up enough to burn, you don't know what it is, what caused it or when it might happen again. If it cannot be verified 100% I would be replacing it. Not the best or cheapest option but I don't like burning surprises in the middle of the night. Good luck.
Thanks to all who tried to help; that's why I love this forum. I was able to find a replacement motor within a short drive. I installed it this morning and closely inspected all other wiring and components while I had everything apart again. Everything looks good. The furnace is now working like it should with no off smells coming through the registers or near the furnace. I will take every opportunity I can to run the furnace while I'm awake to watch it. I don't absolutely need to run it overnight until Tuesday.


On a positive note, I now know that I can remove, completely disassemble, reassemble, and install the furnace in about 2 hours.
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Old 03-23-2023, 11:24 AM   #14
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On a positive note, I now know that I can remove, completely disassemble, reassemble, and install the furnace in about 2 hours.

Your hired!
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Old 03-23-2023, 01:44 PM   #15
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So happy for you that it sounds fixed! That motor is a lot cheaper than a whole new unit, and the knowledge you gained (as well as for everyone following or coming across this post) is priceless.
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