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RVLady_net's avatar
RVLady_net
Explorer
Aug 27, 2016

Coleman Mach thermostat ticking A/C won't come on

1998 Winnebago Brave SE
Problem: AC compressor will not turn on. Coleman Mach thermostat ticks when in the a/c position. When first turned on, the compressor "thuds" like it wants to come on and then doesn't.It only makes the thud sound one time. Turning it on/off produces no noise.
Fan works great.
Plugged into shore power 110 - reacts same as when on genny (Onan 4000) 30 amps.
There is no start capacitor on this model.
Model No. 7335C896
Reset circuit breaker several times. No help there. But that can't be the problem since the fan works . . . right?
I've checked power on A/C unit itself, but can't get reading between C & R terminals with a/c unit either off or on. That said, I'm no electrician and may be using voltage meter incorrectly, but I don't think so. But having someone else check it today, as well, to confirm.
Question: is this a/c unit simply done or is it a thermostat issue? Is the fact that the thermostat clicks indicative of something?
Class A
  • RVLady_net's avatar
    RVLady_net
    Explorer
    Aug 27, 2016
    Thanks for answering the call. I made a video of the air conditioner and posted on my youtube channel . . here's the link https://www.youtube.com/watch?v=kdLA1RVxDuo

    I do this, just in case, looking at it helps resolves some questions.
  • dougrainer's avatar
    dougrainer
    Nomad
    Aug 27, 2016
    The top black is the start relay. The Capacitors are below it. You test a compressor with NO POWER and wires removed. For kicks, just replace BOTH capacitors. If that does not fix it the compressor is locked up. 20 year old unit----replace the upper unit. Doug
  • RVLady_net's avatar
    RVLady_net
    Explorer
    Aug 28, 2016
    Doug: Of course, after I put the shroud back on, I learned that I did the compressor test wrong. I was shopping for all the replacement capacitors on Amazon. They seem generic to Coleman A/C units, not to mention inexpensive. I was thinking I would do that, just replace them all. And, then if nada, just order a new A/C unit . . . but what to get? Because my a/c unit has no markings or I guess more accurately the metal plate that is suppose to contain the information is blank, I don't know if it is a 15,000 BTU or !3,500 BTU or what? My RV is 26' feet and ducted. So, of course the ducted units cost more! LOL I just don't want to blow the ducts out! LOL Thanks for all your help. I sincerely appreciate it.
  • dougrainer's avatar
    dougrainer
    Nomad
    Aug 28, 2016
    RVP did not make 15k your year. Ducted models, there is no such thing. The TOP units are ALL the same. Ducted is the Inside plenum package. Usually, when the Start Capaitor fails, you will not get that Umph at the compressor. That Umph is a locked up compressor. You can install a 15k and I would when replacing. You cannot blow out the ducts:B Use this link to determine your correct replacement. Doug

    http://www.airxcel.com/coleman-mach/service-support/model-number-changes
  • RVLady_net's avatar
    RVLady_net
    Explorer
    Aug 28, 2016
    The metal label on the side of the upper unit bears no information, so I'm somewhat guessing as to the exact unit. In the owner's packet, there is a RVP consumer registration card bearing the information I'm forced to work with. Does it really matter which manufacturer I use for a replacement? All the a/c units I've looked at online components seem all the same. The replacement model for my a/c unit is a unducted model until you buy the duct kit. Is this what you mean by 'ducted models, there is no such thing."? And, as to the compressor, does it fail all at once? Works one time but not the next? I've read where they fail slowly. Is that wrong? Doug, thanks again for your valuable input/help.
  • dougrainer's avatar
    dougrainer
    Nomad
    Aug 28, 2016
    RVLady.net wrote:
    The metal label on the side of the upper unit bears no information, so I'm somewhat guessing as to the exact unit. In the owner's packet, there is a RVP consumer registration card bearing the information I'm forced to work with. Does it really matter which manufacturer I use for a replacement? All the a/c units I've looked at online components seem all the same. The replacement model for my a/c unit is a unducted model until you buy the duct kit. Is this what you mean by 'ducted models, there is no such thing."? And, as to the compressor, does it fail all at once? Works one time but not the next? I've read where they fail slowly. Is that wrong? Doug, thanks again for your valuable input/help.


    1. Compressors can lock up and then when the outside temp changes can then run. Then lock up again.
    2. The TOP AC units are all the same. DUCTED has to do with the inside plenum package. When you went to the RVP website, it states what to purchase and use with the current upper replacement model.
    3. NO, you cannot change Brands without buying more parts. As far as I am concerned, there are only 2 GOOD long term makers of RV AC units. Dometic(Duotherm) and RVP(Coleman). Use other brands at your own peril.
    4. RVP has 2 places for the model number. 1. On the top by the capacitor plate and from the inside on the round metal mount tray. There is a model sticker at both locations. Same with Dometic. Doug
  • RVLady_net's avatar
    RVLady_net
    Explorer
    Aug 28, 2016
    Your description of 'lock up' seems right-on. That's what it seems to do. It makes a noise like it 'wants' to come on and then locks up. Since the heat has abated in my area, I'm going to take a wait/see if any come up on sale! Thanks so much again. I have subscribed. The information you've provided is solid and I'm looking forward to learning more from you.

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