COMPRESSOR MOTOR OPEN OR SHORTED WINDING MEASUREMENT PROCEDURE
|Turn power off. Use the capacitor discharge tool (Figure SP-8-6) to discharge|
the start and run capacitors and any other capacitors that may be used in the
unit. Locate the wiring connected to the compressor motor windings and start
circuit. (Refer to the unit wiring diagram.)
|The wiring related to the compressor motor and its starting circuit is identified. All
high-voltage capacitors used in the equipment are discharged, including the run
and start capacitors.
|10. Isolate the compressor from the remainder of the circuit by disconnecting the|
compressor motor leads from all the related components, including the run
and start capacitors and start relay.
|Compressor motor leads are disconnected from other components to measure
compressor motor resistance only.
|11. Check the compressor motor for shorted or open windings as follows:|
Set up the VOM/DMM to measure resistance on the R x 1 ohm scale. If using
a VOM, make sure that it is zeroed. Connect one lead of the VOM/DMM to
one of the three motor leads as shown in Figure SP-9-15. Touch the other
meter lead to the remaining motor leads, one lead at a time, and observe
the meter indication.
|VOM/DMM indicates a measurable resistance for both measurements. Check
compressor motor for grounded winding per step 12.
VOM/DMM indicates zero resistance for one or both measurements. This indicates
a completely shorted winding. Replace the compressor.
VOM/DMM indicates infinity for one or both measurements. This indicates that
one or more motor windings are open. If checking a compressor with an internal
motor protection device, make sure the compressor has had adequate time to
cool off so that the protective device has reset. It may require an hour or more
after the motor has been turned off before the internal protection device resets.
Replace the compressor if the compressor is cool and the internal protection
device has not reset.
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