Compressor Electrical Diagnostics - Manitowoc I0320 Technician's Handbook

COMPRESSOR ELECTRICAL DIAGNOSTICS

The compressor does not start or will trip repeatedly
on overload.
Check Resistance (Ohm) Values
Compressor windings can have very low ohm
NOTE:
values. Use a properly calibrated meter.
Perform the resistance test after the compressor
cools. The compressor dome should be cool enough
to touch (below 120°F/49°C) to assure that the
overload is closed and the resistance readings will be
accurate.
SINGLE PHASE COMPRESSORS
1. Disconnect power then remove the wires from the
compressor terminals.
2. The resistance values between C and S and
between C and R, when added together, should
equal the resistance value between S and R.
3. If the overload is open, there will be a resistance
reading between S and R, and open readings
between C and S and between C and R. Allow the
compressor to cool, then check the readings
again.
160 Part Number STH038 5/12