# THREE-PHASE COMPRESSOR MOTOR WINDING-TO-WINDING RESISTANCE MEASUREMENT PROCEDURE

StepExpected Result/Action
14. Check a three-phase compressor motor for winding-to-winding shorts or
partially shorted windings as follows:
Because of the extremely low resistance values being measured, an accurate
VOM/DMM must be used to perform this step, otherwise a good compressor
may be judged as bad. Connect the VOM/DMM across the leads connected to
the compressor terminals T1 and T2, then measure and record the resistance
as shown in Figure SP-9-18.
Repeat the resistance measurements between the leads connected to
compressor terminals T2 to T3 and T3 to T1.
VOM/DMM indicates a measurable resistance across each winding. As a rule of
thumb, the motor windings are usually judged to be good if the resistance
measured across each winding is nearly identical to that of the other two
windings.
Example 1
Assume that the resistances measured across the three windings are 5 ohms, 4.99
ohms, and 5. J ohms. In this example, the motor windings would be judged to be
good because the three motor resistances are nearly identical.
Example 2
Assume that the resistance measured across the three windings are 5 ohms, 4.99
ohms, and 3.0 ohms. In this example, the motor windings would be judged to be
partially shorted because one of the resistances (3.0 ohms) is significantly
different than the other two.