192 Part Number STH025 8/12
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.
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