Question about Coleman Mach 15 Air Conditioner

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Compressor on my RV coleman ac unit bogging down

When I turn my AC unit on it runs fine and cools down my RV. After 1st cycle the compressor sounds like it is trying to kick in but after about 40 seconds it stops and only the fan runs. About 3-4 minutes later the compressor tries to kick in but the same thing happens. This goes on and on unless I turn the ac unit off for about an hour and then when I turn it on it will work fine but only through the 1st cycle. Do I have a compressor issue? Do I need to buy a new unit?

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  • rwetzel56 Jun 29, 2009

    I'm not sure about head pressure or thermal breaker tripping. All I can tell you is that the unit bogs down after the first cycle. The unit cools down the first time but after that the unit won't cool down, it just tries.

  • rwetzel56 Jun 30, 2009


    I noticed yesterday when testing this unit again, during the day when it is hot the unit ran fine. When it cools down in the evening, I noticed the unit wants to do this recycling thing. The fan on the unit runs when the compressor kits on and off. During the heat of the day the unit cools the camper and then shuts down and restarts fine when the thermostat calls for it. This is what has me puzzled. The amps are around 12.3 - 14.4 as the compressor runs and then it drops to 2.2 -2.3 when only the fan is running. Haven't checked the capacitor yet but will do that as well.

  • rwetzel56 Jun 30, 2009

    Also, it is a 15,000 BTU unit made by Dometic Durotherm and not a Coleman.

  • rwetzel56 Jul 01, 2009

    Also, it is a 15,000 BTU unit made by Dometic Durotherm and not a Coleman.

  • Ned C Cook
    Ned C Cook May 11, 2010

    excessive head pressure on ac pump.or thermal breaker tripping.



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Take a look at your start capacitor. This the capacitor that kicks the compressor over when it tries to start. If the capacitor is bad, it cannot kick the compressor back over after the first cycle because the head pressure has not evened out yet. It is located in the upper unit on the side panel in a small box. Be careful, highly charged capacitors can zap you if you are not careful. Disconnect power and touch across the terminals with a meter or a screwdriver to discharge the capacitor.

Hope this helps,


Posted on Jun 29, 2009

  • Jeff Myers Jul 04, 2009

    Ok, the dometic units have the same start capacitor as the colemans. It is odd that it only does this in the evening. It cannot be a bad compressor if it works fine during the day. This is actually completely opposite of what usually happens on these units. The other it may be is a defective freeze control switch. The cold control is normally open (no continuity), and closes when the temperature of the evaporator is below 41 to 49 degrees. The switch will return to open at 52 to 62 degrees. So at temperatures above 62 the switch is open, below 41 it will be closed. If the parameters of your cold control are out of range, that would explain why it is doing it at night when the ambient temperature is greatly reduced. When you get a chance, take the cover off of the control box (in the return air of AC) and unplug the cold control. It is usually two white wires coming from above and plugged into a blue terminal on the board. If the unit runs fine that night, then you need to replace the freeze control.


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What does it do when powered by the generator? Or is this happening with 110? Do you have an invertoer on the system? 12v to 110? The reason is power supply issues. What happens on shore power? Any problems then? Has the unit been serviced or worked on recently? Is the fan outside (condensor fan) working? If it isn't it will cause high head pressures. Go topside and verify it is working, it can relly overtax the compressor.- good luck

Posted on Jun 29, 2009


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