[gregoman1]

Coach # 439 1997 45'

Been reading some posts about the Newell basement AC units. I have owned my coach for 12 years and never really had many problems with the AC's other than in our Texas heat they have a hard time in the heat of the day. Have always just had them serviced at the factory or at the RV repair shop I use here in Ft. Worth. I have a problem now, the rear unit will not function and throws the breaker (in main breaker box) as soon as you turn it on. My owners manual indicate the units were manufactured by RVAC Inc. in Coppell,TX.. Obviously they are out of business. Do any of you know anyone that is familiar with these units and can work on them, or can a regular HVAC Tech. work on them? Have also been reading were some of you are upgrading to new units. Just seeking a little advice.

Thanks,
Greg McCann

[Richard]

They are serviceable by an HVAC tech IF you can convince them it is not a rooftop unit. Don’t bother with an RV tech. Most components are available, and if not there are substitutes.

Immediate breaker trip indicates a direct short. There could be many reasons for that.

First, do you have a voltmeter with amp reading capability. And are you comfortable using it?
Are you interested in diagnosing the problem?

Do you have the upgraded control boards from Newell?
Have you installed the heavy duty external relays for the compressors?

[gregoman1]

Thanks Richard,

My family owns a semi-trailer repair shop so I have voltmeter and a mechanic that is good with electrical, and yes I would be interested in
diagnosing the problem.

I also have a friend that is a good HVAC man but probably has never seen units like these!

To my knowledge the coach does not have the upgraded control boards or HD external relays, I would have to call Newell and see if that has ever been done,
possibly before I purchased the coach. The person I purchased it from always had it serviced at Newell and I followed that process up until about 5 years ago because of their prices.

Do you recommend adding those when doing these repairs, and will it increase performance?

[Richard]

Here is the readers digest condensed version. The SCS units as built had a serious flaw with the control boards. Issue one was that the current for the compressors traveled through “lands”’ or circuits that were inadequate for the amperage. Second the connection to the board for the compressors was inadequate for a light bulb much less a compressor pulling almost 15 amps at times.

The first fix was to add external relays to remove the compressor current from the boards because at the time there were NO replacement boards to be had. https://newellgurus.com/showthread.php?tid=3252

In recent years Newell had someone make new boards that have robust connections and circuit enhancements. You really need one fix or the other. It will not increase performance, but will increase reliability.

Now let’s get to some basic troubleshooting. You say the breaker trips as soon as the AC comes on. Correct? If correct that tells us the problem is with the Number 1 compressor circuit.

Step one, disconnect all power, remove the circuit board and examine front and back for obvious circuit failure. Post pics of the front and back.

Step two, ohm the windings on the compressor, and both fan motors. That can easily be done where the connectors were removed from the board. https://www.mingledorffs.com/using-an-oh...-windings/

We can go further after seeing the results of those two.