Troubleshooting Capacitors
A defective capacitor may be the cause of the following operating problems:
• Condenser fan will not run.
• Condenser fan will run, but compressor will not start.
• Compressor hums but will not start.
A defective running (or run) capacitor is often the direct cause of the compressor motor cycling on overload. A defective capacitor can be removed and replaced in the field, but first it should be tested to make certain that the capacitor is actually the source of the problem. Before testing the capacitor, inspect it for leaking or swelling. Corrosion around the terminals and bulging caps are caused by leaking electrolytics. These symptoms are an indication of a defective capacitor that can be removed and replaced. There is obviously no need to test it.
Warning
Always completely discharge a capacitor before testing it. This must be done to avoid serious shock injury as well as to protect the testing equipment from potential damage.
Discharge the capacitor by connecting it to a 15,000-ohm and 2- watt resistor, and then disconnect the wires. Check for a ground in a motor-run capacitor by connecting an ohmmeter or test neon lamp in series with the capacitor and the metal part of the case for each capacitor. A ground is indicated if a continuity of circuit exists. Both terminals should be tested to ground, and this must be done with the capacitor disconnected from the compressor.
Replacing Capacitors
When putting a running (or run) capacitor back into a unit, check the capacitor terminals for a marked or identified terminal. The marked terminal may be indicated by a dab of solder, a paint mark, or a stamping on the case. This terminal must always be connected with the wire leading directly back to the contactor. If this capacitor should become defective by a ground, a fuse in the power circuit will blow. If the capacitor is not properly connected, a defect by ground will cause a flow of power through the start-and-run wind- ings before reaching a fuse and cause compressor damage.