Compressor will not come on. Fan runs great.

If it trips the circuit breaker as soon as you turn the FAN on, suspect either a bad fan motor or a failed fan motor start capacitor. If you are able to turn the fan on but the circuit breaker trips as soon as the COMPRESSOR starts, it is possible that the compressor is seized.
If, on the other hand, the unit is tripping a GFCI (Ground Fault Circuit Interrupter) breaker or GFCI utility outlet, it is possible that neutral and hot are reversed at the outlet into which the trailer is plugged (happened to me this year at an RV park).

I would check thermostat first. Remove compressor wire from thermostat and see if that cures starting by itself.

At the compressor connectors you have a live and a neutral phase. The live usually goes to a ptc relay starting mechanism which you can test with a meter. If you can disconnect the relay and check the windings of the compressor from one pin to the other two it will tell you if the compressor is open circuit. It is more often than not an overload fault.

my coleman 7330 fan only runs when ac unit is on and then sometimes shuts off and then restarts

COLEMAN R.V. AIR CONDITIONER SERVICE AND REPAIR QUESTIONS
COLEMAN R.V. PRODUCTS
GO TO rvcomfort.com
Click on RVP (RV PRODUCTS)
Click on type of AC, if you can’t find the information you want there,
then click on contact us on the Green Bar.
You can get Service Support or Email address and Phone numbers.

COLEMAN R.V. AIR CONDITIONER SERVICE AND REPAIR QUESTIONS
COLEMAN R.V. PRODUCTS
GO TO rvcomfort.com
Click on RVP (RV PRODUCTS)
Click on type of AC, if you can’t find the information you want there,
then click on contact us on the Green Bar.
You can get Service Support or Email address and Phone numbers.

Replace the thermostat.

If this is a ducted unit, check the thermostat. It has a fuse for protection that may have blown. If the fuse is fine and you have power to the upper units control box, check for 120V incoming power at the control box and also check for incoming 12V on the Yellow and GH wires when tstat is set to high cool.

Hope this helps.

I had a problem with my coleman mach 3 AC, we were at an RV park up at lake shasta CA and the fan would stay on but the compressor would come on for a few seconds and then trip off. It was the motor overload relay on the compressor that was tripping. the RV park was old and apparently the wiring to the panelboard at the RV park was too small, when you are drawing a lot of current there was too much voltage drop across their line, to make up for this the motor tries to draw more current and heats up the motor overload and it trips off. I solved this problem by buying an autoformer from Camping World, it senses a voltage drop and automatically boosts the voltage.

I am now having a seperate problem, the compressor is either locked up or has too much back pressure and trips off the service breaker when trying to start. The only solution I can see with my current problem is to replace the entire unit.

Try changing out the start up and run capacitors for the compressor.