Manitowoc S300 Technician's Handbook page 153

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.
COMPRESSOR DRAWING LOCKED ROTOR
To determine if the compressor is seized, check the
amp draw while the compressor is trying to start.
The two likely causes of this are a defective starting
component and a mechanically seized compressor.
To determine which you have:
1. Install high and low side gauges.
2. Try to start the compressor.
3. Watch the pressures closely.
A. If the pressures do not move, the compressor
is seized. Replace the compressor.
B. If the pressures move, the compressor is
turning slowly and is not seized. Check the
capacitors and relay.
COMPRESSOR DRAWING HIGH AMPS
The continuous amperage draw on start-up should not
be near the maximum fuse size indicated on the serial
tag.
Part Number 80-1479-3 7/10 153