Diagnosing Start Components - Manitowoc QuietQube Series Technician's Handbook

DIAGNOSING START COMPONENTS

If the compressor attempts to start, or hums and trips the
overload protector, check the start components before
replacing the compressor.
Capacitor
Visual evidence of capacitor failure can include a bulged
terminal end or a ruptured membrane. Do not assume a
capacitor is good if no visual evidence is present. A good
test is to install a known good substitute capacitor. Use
a capacitor tester when checking a suspect capacitor.
Clip the bleed resistor off the capacitor terminals before
testing.
Relay
The relay has a set of contacts that connect and disconnect
the start capacitor from the compressor start winding. The
contacts on the relay are normally closed (start capacitor in
series with the start winding). The relay senses the voltage
generated by the start winding and opens the contacts as
the compressor motor starts. The contacts remain open
until the compressor is de-energized.
RELAY OPERATION CHECK
1. Disconnect wires from relay terminals.
2. Verify the contacts are closed.
Measure the resistance between terminals 1 and 2.
No continuity indicates open contacts. Replace the
relay.
3. Check the relay coil.
Measure the resistance between terminals 2 and
5. No resistance indicates an open coil. Replace the
relay.
158 Part Number: 000015431 Rev01 5/19