Testing Motor Windings

3. Place the meter probes across a load. You should obtain a reading. Place one meter probe on the right side of the LLP and the other probe on the left side of the IT. You should obtain a reading. If you obtain no reading, replace the load. To further increase your understanding of electrical troubleshooting, review the rules you have just read using a different method. The flow charts in figure 14-30(A), and (B) review electrical troubleshooting with a digital multimeter. To use a multimeter effectively and troubleshoot an A/C & R unit electrically, you must not only know the information provided here but also practice by testing c i r c u i t s . A l w a y s r e m e m b e r t o r e s p e ct electricity. Whenever possible, perform your electrical troubleshooting with the power OFF using continuity checks. TESTING MOTOR WINDINGS If, during the procedure for identifying motor terminals, the ohmmeter displays a blank readout during any test, there is probably a defective winding. A defective winding may be classified as an OPEN w i n d i n g o r a S H O R T E D w i n d i n g . T he display will be zero if the winding is G R O U N D E D . T e s t e q u i p m e n t a n d procedures applicable to faulty windings are discussed below. OPEN WINDINGS Open windings can occur in the starting winding, the running winding, or both. An open winding is the result of a burned-out or grounded fault or simply a break somewhere in the lead or winding that prevents the current from completing the circuit. A motor with an open winding does not start. If only one winding is open, the motor hums, but if both windings are open, no sound is emitted nor current consumed. Open windings can be checked by an ohmmeter, a voltmeter, or a test light. Ohmmeter Continuity Test Procedure The procedure for making an ohmmeter continuity test is shown in figure 14-31 and outlined below. Turn the power OFF, discharge all capacitors, and remove the wires from the C-, S-, and R-terminals of the motor. With the ohmmeter set on the lowest scale, check the resistance from C to R, C to S, and R to S. 14-18(E)