Goofy Rear A/C

Mariner · October 29, 2015

My rear A/C/ unit has started having a mind of it's own. Sometimes power will be going into the circuit board but not coming out. And when I turn the A/C on with it on auto, the fan will immediately come on without the A/C compressor kicking in. Then other times it will work normally. Turn it on with it on auto, wait about 120sec. and fan will come on, then compressor will kick in and it blows cold air as it should. It has me pulling out my hair as to what could be causing it. I've checked all wiring and it's all secure, none loose. I finally called out an RV tech who also hasn't a clue. He called Dometic and they have no solution. Any off the wall ideas?

Kirk W · October 29, 2015

My rear A/C/ unit has started having a mind of it's own. Sometimes power will be going into the circuit board but not coming out. And when I turn the A/C on with it on auto, the fan will immediately come on without the A/C compressor kicking in. Then other times it will work normally. Turn it on with it on auto, wait about 120sec. and fan will come on, then compressor will kick in and it blows cold air as it should.

That isn't much information to go on but my best guess would be that there is a problem in that circuit board. Solid state components do sometimes become intermittent in operation. Circuit boards can have a bad solder connection or a crack that sometimes conducts and others does not. From your description, I'd guess that there is some sort of time delay built into the circuit board and it could be sometimes failing to time out. But keep in mind that all of this is only a guess since we do not know nearly enough to make an informed diagnosis.

Unfortunately, there are many RV techs out there who have very little expertise in working on air conditioners.It is very common for RV shops to just replace an air conditioner because they don't know what else to do.

Wrknrvr · October 30, 2015

The RV tech is apparently not an authorized dealer as they will figure out what is happening. I am an authorized dealer and they will figure out what is wrong.

Sometimes it takes some testing, maybe even install a test part but they will figure it out.

Safe Travels, Vern

Mariner · October 30, 2015

Dometic can't figure it out either. The board is a recent(2mos.ago)replacement and has been working fine til now. I guess it could be something with the board. When running, the A/C is fine putting out 48 degree air, so I don't believe it's the unit itself. One of things I hate the most....intermittent problems.

Wrknrvr · October 30, 2015

After reading your post again I noticed power is not always going into the board. If I am on the same thought as what that statement says.

There may be a power diverted control box that will send power to the dryer or rear ac unit, but not both at the same time. That will give symptoms as you may be experiencing. It probably is made by Inteletec. And can be a pain to figure out or to locate as then stick them anywhere.

After that it could the thermostat, then throw in the Inteletec switch problem.

There could be a problem with the energy management system also.

Add them altogether and it could be confusing. Maybe lose another hair or two.

If I Was on the job I would think about applying separate power directly to the incoming power on the ac. I have also powered the fan on good voltage and the compressor to prove they are both working as designed.

Then work backwards through also devices involed to find your problem or problems.

One time I had four meters working on different locations to see what was happening

Safe Travels, Vern