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TM5-4120-377-14
(4) Carefully feel lower part of compressor.
l If air conditioner has been connected to power supply for at least four hours, compressor should
feel warm (100 to 120°F). If not warm, test crankcase heater for continuity.
l If air conditioner has not been connected to power supply for at least four hours, compressor
temperature should be the same as surrounding air temperature.
(5) Using multimeter, test crankcase heater and thermostat circuit at J4 connector:
l 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 J4-F. If open, heater should be replaced.
Check thermostat continuity between open connection and J4-G. If open, thermostat should be
replaced.
(7) Using multimeter, test compressor motor windings.
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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 J4:
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 motor protector is
closed.
Compressor containing shorted, open or grounded winding or open motor protector, should be
replaced.
If compressor windings are bad, check for compressor burn out prior to installing a new
compressor. (See instructions in compressor removal.)
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