Capacitors.

TM 55-1905-223-24-17

Capacitors.

(1) Visual check of capacitor:

WARNING

Turn power OFF and discharge capacitor to avoid electrical shock.

(a) Turn OFF unit power. Use a screwdriver with insulated handle to short capacitor terminals and

discharge them to eliminate the possibility of accidental shock. Remove capacitor wires.

Remove capacitor from unit and visually inspect. A bulged or leaking capacitor should be

considered defective and replaced. Start capacitors usually have a relief plug or disc in their

top. If the plug or disc is missing, it indicates excessive heating.

(b) Replace bulged, leaking, or overheated capacitor.

(2) Checking for shorted or open capacitor:

Use an ohmmeter on the 0-10,000 ohm scale setting.

Place meter probes on capacitor

terminals.

If meter needle dips to zero or a low resistance and then climbs toward a high resistance, the

capacitor is probably OK. If needle dips to zero or a low resistance and stays there, the

capacitor is shorted and must be replaced. If needle does not move, the capacitor is open and

must be replaced.

d. Transformers.

(1) Check transformer as follows:

(a) Use a voltmeter and with the primary supply circuit ON, check the primary or input voltage.

(b) Next, check secondary or output voltage.

If no voltage is available, the transformer is

defective.

(2) Replace defective transformer.

e. Alternating Current Motors and Compressors.

(1) The following procedure will check the condition of a three-phrase motor or compressor.

(a) Use a megohmmeter (megger) for this check.

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