Compressors are an integral part of any air conditioning unit. Compressors pressurize the coolant chemicals inside the a/c unit, causing the chemical reaction that cools down the air that passes through. An improperly working compressor in an a/c unit can cause major operational failure for an air conditioner during use. Troubleshooting your air conditioning unit properly will allow you to diagnose the condition of your a/c compressor.

A/C Won't Cool

Check your compressor if your a/c unit fails to produce cool air while operating. A malfunctioning compressor is the most common cause of an air conditioning unit's inability to cool air. Turn on your a/c unit and note whether you can hear the fan motor. If the a/c unit's fan motor and LED display are operating properly, but the unit will not produce cool air, inspect your compressor to find if it's malfunctioning.

Disassembly

Disassemble your a/c unit to uncover the compressor for closer inspection. You will need to do this in order to reveal the compressor inside the appliance. Refer to your air conditioner's owner's manual for more model-specific instructions about disassembling the casing and any other electronic components. Begin by removing the a/c unit from its power source. Use common hand tools, such as a screwdriver, an Allen wrench and a socket wrench, to disassemble the frame and any other necessary components. Remove the terminal cover to reveal the compressor's wires. You will need to access the wires for continuity tests or compressor removal.

Continuity Test

Use a multimeter to test the a/c compressor for continuity across its terminals. There are three different terminals in most a/c compressors. Commonly, they are labeled C, R and S. Test the continuity between all three possible two-terminal combinations: C and R, R and S, and S and C. Wait for the compressor unit to cool down after operation before beginning the continuity test. If the ohm reading on the multimeter is higher than 30 during any test, and the compressor is cool to the touch, the compressor is bad.

Source:

HVAC For Beginners: Air Conditioner Compressor - A Troubleshooting Guide

RepairClinic.com: Air Conditioner Troubleshooting