Manitowoc

Compressor Electrical DiagnosticsThe compressor does not start or will trip repeatedlyon overload.CHECK RESISTANCE (OHM) VALUESNOTE: Compressor windings can have very low ohmvalues. Use a properly calibrated meter.Perform the resistance test after the compressorcools. The compressor dome should be cool enoughto touch (below 120°F/49°C) to ensure that theoverload is closed and the resistance readings will beaccurate.SINGLE PHASE COMPRESSORS1. Disconnect power from the condensing unit andremove the wires from the compressor terminals.2. The resistance values between C and S andbetween C and R, when added together shouldequal the resistance value between S and R.3. If the overload is open, there will be a resistancereading between S and R, and open readingsbetween C and S and between C and R. Allow thecompressor to cool, then check the readingsagain.CHECK MOTOR WINDINGS TO GROUNDCheck continuity between all three terminals and thecompressor shell or copper refrigeration line. Scrapemetal surface to get good contact. If continuity ispresent, the compressor windings are grounded andthe compressor should be replaced.To determine if the compressor is seized check theamp draw while the compressor is trying to start.176 Part Number 80-01111-9 7/10