The Compressor is the heart of your Air Conditioner. It is a mechanical device that increases the pressure of a gas by reducing it’s volume pumping refrigerant through the lines.
The main reason a compressor would fail to start is LOW VOLTAGE
The compressor could fail in a few different ways
- Shorting out internally
- Faulty Overload Protector
In situations where there is no compressor function we can isolate the problem by bypassing the A/C control board & putting power directly to the compressor
For Coleman Air Conditioners with No Compressor Function you can follow this manufacturer designed Flowchart
The Overload Protector is a normally closed thermal switch that opens if the compressor overheats due to electrical problems such as low voltage or if the fan fails.
It can be found in direct contact with the compressor, or sometimes as an internal component (In which case a failure in the Overload Protector would warrant replacing the top unit)
To test the Overload Protector make sure your breaker is off and check for continuity across the terminals at ambient temperature
A weak Overload Protector could cause the compressor to rapidly turn on and off, also known as short cycling
There is an excellent way of checking compressors by checking the windings, as depicted
C = Common
S = Start
R = Run
Since the start and run windings are connected to the common terminal of the compressor, a simple test with a multimeter set to measure resistance in ohms will determine the electrical condition of the compressor.
To begin with, disconnect all leads to the compressor. Be sure to unplug the coach from electrical power or shut down the generator.
NOTE: Be sure to discharge all capacitors before disconnecting wires.
To discharge, use an AC voltmeter set at the highest AC scale (500V minimum) and connect meter leads to the terminals of the capacitor.
To ensure that the capacitor has dischargd, the leads should be reversed and the procedure repeated.
Now, with the three leads disconnected and marked (including the overload), check and record the following ohm readings at these terminals on the compressor:
S +C (start + common)
R + C (run + common)
S + R (start + run).
Because the start and run windings are both connected to the common terminal, a little arithmetic will yield the answer.
Add the S + C ohm reading to the R + C reading, and the sum should equal the S + R reading.
The equation is: (S + C) + (R + C) = (S + R).
Check with the multimeter for continuity between the case and all terminals. There should be no continuity (infinity) between the compressor case and any terminal.
If there is continuity (no resistance), the compressor is shorted to the case and needs to be replaced.
