Manitowoc SD0672C, Technician'S Handbook

Page: 136 / 298

136 Part Number 80-1505-3 6/11
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:
• Install high and low side gauges.
• Try to start the compressor.
• Watch the pressures closely.
• If the pressures do not move, the compressor is
seized. Replace the compressor.
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.
The wiring must be correctly sized to minimize voltage
drop at compressor start-up. The voltage when the
compressor is trying to start must be within ±10% of
the nameplate voltage.