Diagnosing Start Components; Capacitor; Relay - Koolaire KY0275W 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.
CAPAC
TOR
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 open.
The relay senses the voltage generated by the start
winding and closes and then opens the contacts as the
compressor motor starts. The contacts remain open until
the compressor is de-energized.
Part Number STH047 5/16 97