Compressor Electrical Diagnostics - Welbilt Manitowoc NEO UDE0065A Technician's Handbook

COMPRESSOR ELECTRICAL DIAGNOSTICS

The compressor does not start or will trip repeatedly on
overload.
Check Resistance (Ohm) Values
NOTE: Compressor windings can have very low ohm
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 ensure that the overload is closed and the
resistance readings will be accurate.
Single Phase Compressors
1. Disconnect power from the condensing unit and
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.
Check Motor Windings to Ground
Check continuity between all three terminals and the
compressor shell or copper refrigeration line. Scrape metal
surface to get good contact. If continuity is present, the
compressor windings are grounded and the compressor
should be replaced.
To determine if the compressor is seized check the amp
draw while the compressor is trying to start.
196 Part Number 000014797 Rev02 05/19