COMPRESSOR (Continued)

TM 5-4120-359-14

WARNING

Do not touch heating element.

(4) Carefully feel lower part of compressor.

If air conditioner has been connected to power supply for at least four hours, compressor should feel

warm (100 to 120F). If not warm, test crankcase heater for continuity.

If air conditioner has not been connected to power supply for at least four hours, compressor should be at

ambient temperature.

(5) Using multimeter, test crankcase heater, and thermostat circuit at J10 connector:

Using multimeter, test resistance from pin F to pin G. Resistance should be 950 to 1430 ohms. Lower

reading indicates short, and infinite reading indicates an open.

(6) Using multimeter, test crankcase heater, and thermostat at junction box:

Remove compressor junction box cover.

Open connection between thermostat lead and heater lead.

Check heater continuity between open connection and J10-F. If open, heater should be replaced.

Check thermostat continuity between open connection and J10-G.

If open, thermostat should be

replaced.

(7) Using multimeter, test compressor motor windings

Check continuity between pins A, B, and C and the compressor body. No continuity should exist. If

continuity exists, the compressor is bad.

Test 3 phase windings at J10:

A to B

B to C

A to C

All resistances should be above zero and less than 2 ohms.

Test resistance between pin D and pin E Resistance should be zero indicating thermostatic switch is

closed.

Compressor containing shorted, open or grounded winding or open thermostatic switch, should be

replaced.

If compressor windings are bad, check for compressor burn out prior to installing a new compressor.

(See instructions in compressor removal.)

b. Repair. The compressor and motor assembly are hermetically sealed in a metal canister and cannot be repaired.

The crankcase heater element, and related parts, and the electrical connector are attached to the canister externally and

may be replaced without opening the refrigeration pressure system.

4-179