TM 10-8145-222-23
0004
MAINTAINER MAINTENANCE TROUBLESHOOTING MALFUNCTION/SYMPTOM INDEX
Many of the troubleshooting procedures to be performed will involve either voltage or resistance checks on various
system components. The refrigeration unit microprocessor controller uses numerous plug and play socket type relays
(Figure 1). Each of the plug and play socket type relays is identical in operation and physical makeup. Figure 1
provides a pin out of the relays and a schematic representation of the relay circuitry. Pin 30 is always hot and provides
control power to normally closed (NC) pin 87a or normally open (NO) contact 87, depending upon energized status of
the relay. Pin 86 is always hot and provides power to the relay coil. Pin 85 is the microprocessor control ground.
Figure 1. Relay Pin Out and Schematic.