Compressors become inoperative through either a mechanical or an electrical failure.

Before beginning a compressor test, check the power supply to see if low voltage is the problem. The voltage must be high enough to bring the initial speed up to 75% of its normal revolution per minute (rpm) to allow the run winding to take over. If after start-up this initial speed is never reached, the run winding will never engage, causing the start winding to overheat in a few seconds. When the overload protector senses the high amperage/heat, it shuts off the power to the compressor. When the compressor start winding cools down, the overload protector closes the circuit to the compressor again, and the short-cycling continues. Line voltage may not vary beyond +10% of the compressor specification printed on its nameplate.

Equipment designed to operate between 108 VAC and 115 VAC will not operate well when the voltage drops below 98 VAC. Should this occur, advise the customer to call the power company to remedy the problem as there may be nothing wrong with the unit. There are transformers on the market today that can remedy the low-voltage problem by increasing the supply voltage. Sometimes there are too many pieces of equipment connected to the same receptacle causing a voltage drop below the acceptable range. Just disconnect some of the load and reconnect it to another wall outlet.

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