A refrigerator compressor is one of the most important parts of the refrigerator. It pulls in refrigerant gas, compresses it, and exhausts it to a condenser. The suction side of the compressor pulls in the refrigerant. Compressors only have two valves, and refrigerant flows in only one direction. If you can identify one of the valves, you have identified the other. By identifying the exhaust-side valve, you can quickly find the suction side of a refrigerator's compressor.
Find the condenser on the refrigerator. The condenser is a coil or zig-zag-shaped piece of copper tubing that runs along the back of the refrigerator.
Trace the condenser coil back to the compressor unit. The condenser is connected to the output (blower) valve on the compressor unit.
Find the remaining valve on the compressor unit; this valve is normally right next to the output valve. Since compressor units only have two valves – one output and one intake – the remaining valve is the suction side of the compressor.