Question about Coleman Mach III Air Conditioner

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Coleman roof a/c units compressor not coming on

I recently purchased 2 older coleman roof a/c units. It seem neither ones compressor comes on to provide cold air. Fan motor work fine but when I set the fan speed selector to A/C low or high speed and adjust the temperature selector up or down, the compressor does not come on. What can I do to troubleshoot these units. Could you please lay it out in a step wise format (i.e. check this first and how, then check this and how, etc.). I am a jack of most trades and a master of none, but I am willing to try and most importantly, eager to learn. Thanks, Shawn

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  • note_worthy Feb 01, 2009

    You posted a response on note_worthy@comcast.net but my e-mail address is note-worthy@comcast.net. In response to your questions, the two units are 110 volt. As the model numbers are worn and /or illegible, here is what I come up with: Model # 6753A723 or #67536723 for one and 6799A381. The tech was MrMark52 and I have 2 used coleman roof A/C units and the compressor(s) are not functioning. Help with detailed, step by step troubleshooting instruction. Thanks, Shawn

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  • Master
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Here is a link to the manual for both units,It can be viewed online,save to pc,or printed.

Please rate this a fixya

Posted on Feb 01, 2009

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  • Master
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Hi and welcome to FixYa,

The simplest check would be with a voltmeter. That is checking for the presence/absence of ACV on the compressor when it is supposed to kick in. If yes, then issue maybe with the starting capacitor. The compressor would vibrate but not turn should the capacitor be defective. If no (no voltage present), then the problem could either be with:

  • thermostat;
  • speed selector switch (this is a gang/dual switch, one for the fan one for the compressor on the same switch);
  • control board relay or the board itself (if such is used in your version).
Good luck and thank you for using FixYa.

Posted on Feb 02, 2009

You could always hire a heating specialist to come and check out the AC unit. I had issues with my AC unit and my boyfriend thought he could fix it. He wasn't able to, and ended up doing more damage than there was before. If you aren't sure how to fix it, I definitely recommend getting professional help. That way, at least the problem doesn't get worse.
We Sale and Service Central Air Conditioning Units in Arvada CO

Posted on Aug 12, 2014

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  • Master
  • 11,896 Answers

coleman roof a/c units compressor not coming on - roofairjgif.thumbnail.jpg
Typical picture of mach 3

cover_off.thumbnaicoleman roof a/c units compressor not coming on - fmac20hps-6.gif_mi
fmac20hps-6.gif fm60s.jpg

If you haven't noticed. Pretty much all conditioners are the same concept. They all have compressor, coils, and a power supply. If the unit is not switching on, then the problem usually lies within the power supply components. I would take the cover off the power supply and look for blown fuses,BROKEN RELAY, broken or removed wires, loose solder joints.
With the cover off, have someone else adjust the temp control, while you listen for the compressor to click. do you hear a click? If not then the compressor itself is not getting the power that the fans are getting.

  • Air Conditioner Compressor Stall: One day the front A/C worked, the next day it didn't, and
    there was no obvious low-voltage situation (which will kill an A/C). The fan comes on but the
    breaker trips repeatedly as amp draw gets excessive because the motor won't turn. Both AC units
    (Front: Coleman Mach 9013, 13.5k BTU/hr, Rear: Coleman Polar Cub 9001, 9.2k BTU/hr) specify
    p/n 8333A9021 as the "Hard Start Kit" consisting of a solid-state relay (PTCR), a capacitor, some
    wires, and a strap. Carry a spare ($20) to easily change it yourself or have the parts there for the
    repairman. Check all 120v power connectors for pitting or discoloring, because that's a common
    cause of voltage drops.

  • Mach 3 SPECHS

    Nominal BTU Cooling Capacity 13,500
    Locked Rotor Cooling Amps 54.0
    Running Watts / Cooling 1,595
    Running Watts / Cooling 1,924
    Running Watts / Heating 1,800
    Electrical Rating 155V 60 Cycles
    1 Phase
    Delivered BTU Heating Output 5,600
    Approximate Full-Load Amps / Cooling 14.5
    Approximate Full-Load Amps / Heating 16.0
    Evaporator Air Delivery CFM (highspeed) 320
    Unit Weight (lbs.) 84.5


    Posted on Feb 01, 2009

    • Nate Stansfield
      Nate Stansfield Feb 01, 2009

      Coleman A/C

      Replacement Parts

      7330-3351 Heat/Cool Wall Thermostat

      7330D3211 12 Volt PC Board w/ Relay

      6747A3119 Replacement Motor

      6757B3119 Replacement Motor

      1468A3049 Replacement Motor - 7333 Series

      1468-3069 Replacement Motor - 8333 Series

      25071 Universal Gasket Replacement







    • Nate Stansfield
      Nate Stansfield Feb 01, 2009

      THE RELAY IN THE MACH 3 IS USUALLY THE FIRST THING TO GO!!!!!

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    • Master
    • 1,214 Answers

    Well, first I need to try and find a wiring diagram, so I will need to know model numbers.

    But, the basic circuits are pretty straight forward. I expect these are 120 Volt AC units? Or 12 VDC units?

    Reply back and we'll get it figured out.


    Posted on Feb 01, 2009

    • Mark Egan Feb 01, 2009

      Hello note-worthy.

      Email me at stewartswitch@yahoo.com, and if you would, go ahead and OK on the advice charge. I promise I won't leave you hanging.

      I also responded since our last communications, concerning getting the units charged as you suggested. I do suspect the problem is low charge based on what your saying.

      But will be happy to continue the discussion.


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