If the unit does not run, or if it short-cycles, it can be due to a dead or weak overload protector. An overload protector is mounted on the compressor under the plastic compressor terminal cover. It prevents the compressor from overheating by opening the electrical circuit if it reaches an unsafe temperature (between 225°F and 250°F) during operation. Once the compressor cools to a safe temperature (about 150°F), it closes the circuit and the compressor resumes operation. This is a circuit breaker that needs no manual resetting. (See figs. 55 and 56.)
I. TESTING AN OVERLOAD PROTECTOR USING AN OHMMETER
1. Disconnect the power supply.
2. Remove the plastic terminal cover on the compressor.
3. Remove the two wires connected to the terminals of the overload protector.
4. Set the ohmmeter to the RX1 scale and zero the meter.
5. Touch one probe to each of the wire terminals on the overload protector to get a reading of zero on the meter. If not, replace the defective overload protector.
Also, visually check for cracks on the overload protector. If there are any, the protector is bad and it must be replaced. Sometimes, in spite of the fact that they test OK with the ohmmeter, when they are cool, they may have become weak and open the circuit once they are warm.
II. TESTING AN OVERLOAD PROTECTOR USING THE BYPASS METHOD
(A test wire with two alligator clips will be needed.)
1. Disconnect the power supply.
2. Clip the two test wire alligator clips to the two terminals on the overload protector. Be careful not to allow the clips to touch any other object. Be sure the insulating covers on the clips completely enclose them. (See fig. 56a).
3. Reconnect the power for a short time. Be careful not to touch any part of the unit as there is always the danger of a shock hazard.
4. If the compressor motor starts running without drawing an unusual amount of amperage (this can be checked by a clamp-on ammeter clamped around the wire supplying power to the overload protector), the overload protector is defective and will need replacing.
5. Disconnect the power supply, disconnect the test wire and replace the overload protector.
