Burning electrical smell from furnace

[davidkingham]

I've been dealing with this issue on and off for years, and I can't seem to find the cause. This all started when I replaced the thermostat years ago, and it has continued even with new thermostats.

There is a very strong burning electrical smell (ozone, I believe) coming from the furnace intermittently. Sometimes I can use it for months and never smell it; sometimes, it only happens occasionally, and right now, it's super strong. It seems to be the worst when the furnace has not been used for a while. No, it's not the dusty metallic smell you get when the furnace hasn't been used; this is most definitely electrical; I've shorted enough wires working on cars that I know it well.

A couple of years back, I pulled the furnace and replaced every single component, circuit board, safety switches, etc. The only thing I didn't replace was the blower motor. So this year, I thought surely it has to be the motor, so I replaced that as well. It seemed to help at first, but that could have been coincidental.

I have inspected all the wires and have found zero signs of shorts or melted wires. Where do I go from here? Thanks!

[30sweeds]

Ozone and burn smells are 2 different things. Ozone is created by arcing or sparks,burn is...burn, as in wire insulation.Since you have seemingly checked everything on the furnace,just for kicks,check the shore power breakers for loose,corroded,burnt connections.If you were ever in a low voltage situation,that stuff gets hot and compromises the breakers and connections without tripping the breakers.

[Grit_dog]

^What he said. But lol at running the furnace and “inadvertently “ covering 2/3 of the vents…repeatedly….

That’s like punching yourself in the face repeatedly and it hurts , so you go to the doc and explain what’s going on looking to stop the hurt, yet seem surprised when the doc simply says stop punching yourself in the face!

[dougrainer]

davidkingham wrote:

joebedford wrote:
Welcome to the forum.

You've replaced every component except the blower motor. Could it be .... the blower motor?

Thanks Joe, you missed this: So this year, I thought surely it has to be the motor, so I replaced that as well. It seemed to help at first, but that could have been coincidental.

But, I had a thought last night...there are only three vents in the trailer, and one of them is covered with a rug; occasionally, one of the other vents gets covered with a cat tree if we push it back without noticing. Is it possible the extra resistance in the system would be enough to burn out the motor?

No. The result of restricted ducting is the Hi Limit switch would constantly trip and reset. Motor burn outs are extremely rare. Doug

[MFL]

^ Only three vents, one is covered all the time, one maybe some of the time, is not good. With only 3 vents, I'd make sure none are covered! It will be hard on the blower motor, and create excess heat being trapped in the system.

You may have found the problem, but in any case I'd not block any vents, when running the furnace.

Hope it is this simple! 🙂

Jerry

[davidkingham]

joebedford wrote:
Welcome to the forum.

You've replaced every component except the blower motor. Could it be .... the blower motor?

Thanks Joe, you missed this: So this year, I thought surely it has to be the motor, so I replaced that as well. It seemed to help at first, but that could have been coincidental.

But, I had a thought last night...there are only three vents in the trailer, and one of them is covered with a rug; occasionally, one of the other vents gets covered with a cat tree if we push it back without noticing. Is it possible the extra resistance in the system would be enough to burn out the motor?

[joebedford]

Welcome to the forum.

You've replaced every component except the blower motor. Could it be .... the blower motor?

[davidkingham]

It's a Suburban 2390 SF-25FQ, the trailer is a 2016. I have never smelled it outside, but I'll double check the next time I smell it inside. It is not coming out of the vents, only directly around the furnace, which is below the range/oven. The furnace works well otherwise. With a previous thermostat it was turning off before reaching the set temp, and I would have to cycle it to get it to come back on. But I don't think that has happened since putting in the Micro-Air EasyTouch RV thermostat. Blower works fine, no weird sounds. I have noticed the temp of heated air doesn't seem as warm as it used to be. I've fully inspected all the wires and have found zero signs of burning or melting. Thanks for the help Chum!

[Chum_lee]

What is the year, make, and model of your furnace? (Atwood, Suburban, Dometic, etc.) Do you get this electrical smell on the inside of the coach, the outside, or both, from the hot air vents, or somewhere else? Does the furnace work properly? (aside from the smell) Do you hear any squealing/squeaking when the blower motor runs? (if it does) Do you have any burned wires/multi point connectors inside (or directly outside) the furnace box?

Chum lee

[davidkingham]

midnightsadie wrote:
could be a dead rodent cooking. sure its not batteries cooking. wish could help lot of could be,s

I don't think so, it's a pretty distinct smell, and I just had furnace out and cleaned everything out

[davidkingham]

opnspaces wrote:
I'm trying to come up with an idea where you might be getting the smell. Maybe check around where the furnace is in the coach for something else that might be burning. Could it be happening only when you are running an inverter?

No, it definitely happens without the inverter on, usually first thing in the morning when the furnace kicks on and I never keep the inverter on at night.

opnspaces wrote:
Check the water level on your battery(ies). If the water is really low and if your batteries are hidden inside the RV like behind a panel you might be smelling that overcharge.

No, I have lithium.

opnspaces wrote:
Start paying attention to what the system was doing in the ten minutes before the furnace started. Could the smell possibly only occur when you are on shore power but never occurs on batteries alone? If so could your converter/charger be having the burning smell and the furnace happens to suck the smell into the intake?

It's happened on shore and off.

opnspaces wrote:
Do you ever get that smell when the furnace is not running? Could it be the back of the refrigerator overheating and burning the wood behind the refrigerator? Next time you smell it go outside and open the refrigerator panel and the water heater door and see if the smell is there too.

Nope, never have the smell otherwise.

opnspaces wrote:
Good luck with it and welcome to the forums

Thank you for the warm welcome!

[midnightsadie]

could be a dead rodent cooking. sure its not batteries cooking. wish could help lot of could be,s

[opnspaces]

I'm trying to come up with an idea where you might be getting the smell. Maybe check around where the furnace is in the coach for something else that might be burning. Could it be happening only when you are running an inverter?

Check the water level on your battery(ies). If the water is really low and if your batteries are hidden inside the RV like behind a panel you might be smelling that overcharge.

Start paying attention to what the system was doing in the ten minutes before the furnace started. Could the smell possibly only occur when you are on shore power but never occurs on batteries alone? If so could your converter/charger be having the burning smell and the furnace happens to suck the smell into the intake?

Do you ever get that smell when the furnace is not running? Could it be the back of the refrigerator overheating and burning the wood behind the refrigerator? Next time you smell it go outside and open the refrigerator panel and the water heater door and see if the smell is there too.

Good luck with it and welcome to the forums

[dedmiston]

Welcome to the forum David.

Everyone else: This is his first post. Please be kind and helpful.

As my boss told me a few months ago: "Do me a favor today and please don't be your usual self."