Air conditioner not blowing any cold air.

OK, controls like an old "Window Shaker" - Two Knobs: 1. On/Off Fan/Cool and 2. Cooling Temperature.

Are you comfortable working on electrical stuff that will probably lead you to the roof? Do you have a Meter and/or a Non Contact Voltage Tester. Those NCV testers are really handy. With one, you can test if there's power INTO and OUT OF both the Select Switch and the Thermostat.

First,take all power off the RV and make sure you have all tight connections at the Breaker Panel. You probably do, since FAN works but not A/C.

If you have power into the thermostat and not out, you can certainly bypass it like towpro suggested.

If you have a Meter, will it test Capacitance? Do you have a meter that'll measure AC Amps? Next step, to the Roof for more testing...

Mine is controlled by knobs on the lower AC unit on the ceiling.

towpro wrote:
But I have mine hooked up with a wall thermostat that controls the AC now. (thermostat controls a relay, that switches 120V going up to AC).

What Relay did you use?

OP... It makes a big difference in troubleshooting, whether this Coleman Mach A/C is controlled by wall thermostat, or control knobs in the interior ceiling part of the unit. Which do you have?

I would expect the Simple surburban (non digital thermostat) on wall only controlls the heater.
And the AC controls are up on the AC roof shroud.

The thermostat on the AC roof shroud is a POS if its anything like mine. Mine would not cool lower than 80 deg when set to lowest position. dealer says "all it needs is an adjustment, little screw on thermostat" ya right. Its broke.

But I have mine hooked up with a wall thermostat that controls the AC now. (thermostat controls a relay, that switches 120V going up to AC).

The thermostat in the AC can be tested. it has 3 wires going to it.
1) 120V
2) to compressor
3) to Electric heat grid (if you have that option)

to access thermostat, remove ceiling panel (4 screws). remove access panel to thermostat switch.

with RV 120V power unplugged, you can check resistance between 120v and compressor. when thermostat turns on, meter should go to 0.
or you can test if the thermo is switching 120V to compressor.
or you can just jumper around the Thermostat connecting the 120V to compressor wire.

Check the AC capacitors up top.

Thanks.. we certainly are glad we made the move out here. Still trying to figure out what season we like best. With the trees turning fall is looking pretty good but hoping for a big snow year.

I just have a simple Suburban (non digital) thermostat with a single lever on top to turn it on and adjust the temp. I didn't see anything on there that would allow me to shut off or turn on the compressor. Thanks for the tip though Lambo. I spent the night in your town just two weeks ago. Great place.

Bart

On our lance the thermostat has settings that will turn off the compressor so that only the fan runs... Found that out the hard way:( Not sure if that applies to your thermostat but if it does at least the "fix" is cheap.