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Refrigerator starting relay, starting Capacitor and overload Protector.

Starting Relay

The compressor motor employs both a start and run winding. The run winding is energized during the complete cycle of operation, whereas the start winding is energized only during the starting period. The current-operated type of relay has a coil connected in series with the run winding of the compressor. Some current-operated relays plug directly onto the compressor while others do not. Most relays are mounted in a case located on the compressor. When the thermostat closes, the compressor attempts to start, drawing heavy current through the run winding and the relay coil. This strong current flow through the relay coil creates a magnetic field strong enough to cause the start contacts to lift and close, energizing the start winding. When the compressor reaches approximately 3/4 running speed, the current flow through the relay coil decreases (due to the countering electrical magnetic field in the motor) and as the magnet weakens, the start contacts fall open. This type of relay must be used with an overload protector and must be mounted in an upright position, so that the contacts can fall freely to the "open" position.

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Overload Protector

The bimetallic overload protector is mounted in series with the motor windings. Should the current in the motor windings increase to a dangerous value, the heat developed by the passage of the current through the protector will cause it to open. This breaks the circuit to the motor windings and stops the motor before any damage can occur.

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Starting Capacitor

The starting capacitor (when required) is momentarily placed in series with the start winding to increase the starting torque of the compressor. The starting capacitor drops out of the circuit as soon as the start contacts fall to the "open" position.

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Testing the Capacitor

Before testing the capacitor, disconnect the power supply and place the capacitor in a Capacitor Analyzer. If an analyzer is not available, follow the procedure below.

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Ohmmeter Test

Before testing the capacitor, disconnect the power supply and remove all wiring to the capacitor. Discharge the capacitor using a 20,000-ohm, 2-watt resistor, by placing the resistor across the capacitor terminals. Set the ohmmeter on the highest resistance scale and attach the leads to the capacitor terminals. The needle should deflect instantly toward zero and return slowly to infinity. This should occur each time the leads are reversed. This indicates the capacitor is not shorted or open. If the needle stays at or near zero or remains on infinity, the capacitor is defective and should be replaced. Be sure to reverse leads and check again before condemning the capacitor.

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Disclaimer: The information contained on these pages should never be relied upon as a repair guide or be used to make repair decisions.