Looks like I lost the rear heat pump

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Back2PA

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I've got two heat pumps, and the last few days I've noticed what seemed like either that hot dust smell you get when you fire up the furnace the first time in awhile, mixed with a very faint electrical smell, so faint it never reached alarming, just hmmm? Then there would be no smell for a couple days. Ducted ACs so had some trouble narrowing it to front or back as I got a little residual smell either way.

Well now I know I guess, as the rear unit has quit. Based upon the smell something was getting hot that was in the closed loop air stream, don't know what sort of electrical component would have air passing over it where I would get the smell, seems like the only thing in the airstream would be the heat exchanger but I have only an overview understanding of the heat pump operation.

Thermostat seems to work fine, as does the front heat pump and furnace. (Good thing, going to be 29 tonight.)

Does this sound like a little fried part I can replace, or something else?

Thx
 

Laura & Charles

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Could be anywhere. Originally from Ohio. Go Bucks!
Our rear rooftop unit went out with same electrical/burnt smell you describe. Was summer so I associated it with AC, not heat pump. Compressor was bad and, whatever the issue, not repairable.  My understanding is the compressor is used for both cooling and heating functions.  (Not sure the cost to have it replaced... just one of the many times we’ve been thankful for buying the extended warranty.)
 

Bjwinspect

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Lynchburg Va
Confirm if the outside heat pump unit is actually running.  Heat pumps have coil heaters which supplement the heat output  from the compressor if needed
  If the thermostat is set to "emergency heat" only the coils are used for heat and not the compressor.  These coils can give a burning odor.  Next, if the outside unit is running, try and determine if the refrigerant lines are warm, indicating the compressor is working.  With a bit more info can troubleshoot
 

UTTransplant

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Cedar Falls, IA
Back2PA said:
Thermostat seems to work fine, as does the front heat pump and furnace. (Good thing, going to be 29 tonight.)
Thx
Since you mention the furnace, I assume that is the only unit you will be running at 29 degrees. I was told by a RV service guy a few years back that running a heat pump was harder on the unit than running the AC, and, of course, heat pumps don?t work at much below the mid 40s. I will say that some of the other things that tech told me were pretty dubious, but ...
 

cavie

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Bjwinspect said:
Confirm if the outside heat pump unit is actually running.  Heat pumps have coil heaters which supplement the heat output  from the compressor if needed
  If the thermostat is set to "emergency heat" only the coils are used for heat and not the compressor.  These coils can give a burning odor.  Next, if the outside unit is running, try and determine if the refrigerant lines are warm, indicating the compressor is working.  With a bit more info can troubleshoot

The compressor runs in both Cool and Heat. A heat pump systems uses the compressor to do both. There is a reversing valve involved that recverses the flow of freon. Deispates the heat INSIDE in heat mode and OUTSIDE in cool mode.
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Back2PA

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The rear unit seems to be completely dead, will not run in any mode.
 

Back2PA

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Alpena Jeff said:
That sucks.

Yep. Now that I'm selling it and the extended warranty has run out, I cringe with every new noise  :-\

Mobile repair may be able to make it today. He started off saying "it could just be a lockout circuit or burned capacitor" until I told him the unit would not even run the fan. "Oh, you've got bigger problems then."  :(
 

Back2PA

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I started looking for a mobile tech and there are none in the immediate area. Some friends were helping me search and found a highly rated mobile RV tech an hour away. Called them this morning, they said they thought they could fit me in this afternoon. Sure enough, we rendezvoused a little after three and then proceeded another 1/2 hour to the very remote camp I'm currently in (this after already driving an hour). Pickup pulling large trailer with a neat, well equipped shop. They're up on the roof and within 5 minutes have identified the issue: main power wire burned completely through. They had enough slack to cutoff the burned part of the wire, put it all back together, load tested the compressor, checked heat pump output temps and all was good.

His theory is that several things took place. First, the temp sensors that are supposed to shutdown the heat pumps at a little over 40 degrees apparently wear out, and when they do they allow the heat pumps to stay on at temps colder than design. (I commented in another post that mine worked down to about 30 degrees, I thought I just had some really good heat pumps but actually I already had bad parts.) Second, road vibration probably loosened an electrical fitting. Finally, the extra amperage I was pulling making the heat pumps work outside of design temps, coupled with a loose connection, caused very hot wires that burned completely through. Frankly I'm probably lucky I didn't have a fire.

After all of this, total charge including service fee: $202. Have left reviews here, at RV Service Reviews, Yelp where my friends found the company, and on Google where they have a rating page. The company is American Dreams RV Service out of Lake City, FL. Highly, highly recommended!  :)) :))

(I am still amazed that out in the middle of nowhere I was able to get service at all, same day service on top of that, and exemplary service as icing on the cake. I'm a happy camper!  ;D ) 
 

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