Wiring Diagrams

TM 55-1905-223-24-17

WARNING

Turn power OFF to the motor or compressor to avoid personal injury.

(b) Turn all power OFF to the motor or compressor.

(d) Attach one megohmmeter lead to motor or compressor frame (ground). Make sure you have a

good, clean ground.

(e) Attach the other megohmmeter lead to one of the motor or compressor terminals.

(f) Use the following procedure to check each phase of lead to ground:

Turn the megger handle for at least 60 seconds. Note the meter resistance values at the 10-

second interval and at the 60-second interval. These readings must be higher than 5.0

megohms.

Divide the 60-second reading by the 10-second reading. The result must be 1.15 megohms or

higher.

If the result is lower than 1.15, or if megger readings were lower than 5.0 megohms, the motor

or compressor is defective and must be replaced.

(g) Check each motor or compressor terminal by repeating steps (d) through (f) of this procedure.

(h) Check phase-to-phase conditions as follows:

Attach the megger leads to two of the motor or compressor terminals.

Conduct procedure given in step (f) of this procedure.

Repeat this procedure to check between each set of terminals on the motor or compressor.

2-15. Wiring Diagrams. Wiring diagrams are the maps of electrical circuits. You must understand them in

order to determine where your components are located electrically.

a. Before you make a connection or attempt to locate the source of an electrical problem, you must also

know the following:

(1) What the circuit is suppose to do, and how.

(2) What function is performed by each component in the circuit.

(3) What the physical location of each component is.

(4) The interrelationship of the components.

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