Compressor wire burning in two

We have a 2014 Big Country with a front and rear Dometic unit. Both were replaced in 2016. The rear one was again replaced by Lazy Days in Tucson (under warranty) in 2017. Now the front unit has stopped working. Inspection revealed that the blue wire going to the compressor is burned in half. I temporarily patched it by splicing them together, but again it burned through. Contacted Dometic who told me to take it to one of their dealers. Would replacing the wiring harness solve the problem? I can order one on line. Any ideas what might be causing the burn through? Thanks for all for reading and responding.

I'm no electrician, but it sounds as if you might have an unfused line that is shorting out. Replacing the wire isn't fixing it, you will need to locate the short if there and repair/replace.

According to page 12 of this manual from the Heartland Forum Library, the Blue wire is the main power wire going into the compressor.
http://manuals.heartlandowners.org/...LCD with separate control box_3314378.000.pdf

It first goes through the overtemperature switch (normally closed) on top of the compressor. I would say you have a shorted compressor, but am at a loss as to why your circuit breaker did not trip, unless the blue wire conductor could not carry the current. Maybe the breaker should be replaced once the AC is fixed. The breaker is supposed to be an air conditioning type, 20 amps. The normal running current of a good 15K BTU Dometic air conditioner is a little below 13 amps.

wdk450 said:

According to page 12 of this manual from the Heartland Forum Library, the Blue wire is the main power wire going into the compressor.
http://manuals.heartlandowners.org/...LCD with separate control box_3314378.000.pdf

It first goes through the overtemperature switch (normally closed) on top of the compressor. I would say you have a shorted compressor, but am at a loss as to why your circuit breaker did not trip, unless the blue wire conductor could not carry the current. Maybe the breaker should be replaced once the AC is fixed. The breaker is supposed to be an air conditioning type, 20 amps. The normal running current of a good 15K BTU Dometic air conditioner is a little below 13 amps.

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When the compressor in one of the a/cs in our 2014 Big Horn, the mobile tech said it was best to just replace the unit, as the newer one are better and more efficient. He was right because there was a world of difference between the old one and new one.

pegmikef said:

When the compressor in one of the a/cs in our 2014 Big Horn, the mobile tech said it was best to just replace the unit, as the newer one are better and more efficient. He was right because there was a world of difference between the old one and new one.

Click to expand...

By federal law, RV air conditioners are not to have their refrigerant system opened for servicing. There are no fill or gauge ports. If there is a problem involving the refrigerant system the unit HAS to be replaced.

Thanks for the replies and suggestions. Our AC man examined the unit and determined the blue wire was too short at installation, was not properly connected to the terminal and had corroded badly. He removed the entire wiring harness, reconnected a new one (after extensive cleaning of the terminal) and wrapped the connection in shrink wrap. We are in Florida. So far, so good. Unit is cooling good. Breaker is cool to the touch. You guys have all the answers. Thanks and safe travels.

wdk450 said:

By federal law, RV air conditioners are not to have their refrigerant system opened for servicing. There are no fill or gauge ports. If there is a problem involving the refrigerant system the unit HAS to be replaced.

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Unless the law has changed in the past few years a RV air conditioner is no different than servicing a window AC unit. Household refrigerators/freezers, window AC's, dehumidifiers, ice makers, etc. all have sealed systems, but can be repaired by a certified refrigeration tech. The only limit to entering the sealed system by a certified Refrigerant technician is the cost to the customer as the cost of repair does not warrant the value in return. Replacing a defective compressor on a window AC or a RV rooftop AC could easily run as much or more as purchasing a new unit.

jerryjay11 said:

Unless the law has changed in the past few years a RV air conditioner is no different than servicing a window AC unit. Household refrigerators/freezers, window AC's, dehumidifiers, ice makers, etc. all have sealed systems, but can be repaired by a certified refrigeration tech. The only limit to entering the sealed system by a certified Refrigerant technician is the cost to the customer as the cost of repair does not warrant the value in return. Replacing a defective compressor on a window AC or a RV rooftop AC could easily run as much or more as purchasing a new unit.

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I stand corrected, and was just posting what I thought I recalled from all of my previous RV repair online reading.

The legal part is reflected by your post. The average shade tree mechanic is NOT supposed to open up the refrigerant section. You have to be a certified refrigeration tech who has passed the EPA certification test, and who has the thousands of dollars of maintenance equipment like valve/gauges, refrigerant recovery system, a high vacuum pump, nitrogen, and more.

BTW, while researching this reply, I came across the best RV owner rooftop air conditioner website I have seen. I am going to bookmark this one: https://axleaddict.com/rvs/How-To-Service-And-Repair-A-Motorhome-Air-Conditioner-AC

I had mine burn up. I choose to replace the whole unit as I figured it was a fire hazard and something was wrong with the start cap. I could not pull it out to inspect.