TM 10-8145-222-23
0078
REPAIR CONTINUED
Test Relay
NOTE
The plug and play socket type relay used in the MPC box is tested using a 9-volt DC
battery. When power is applied to the relay, an audible click will be heard if the coil is
operating correctly.
1. Pull defective relay (Figure 1, Item 3) out of relay socket (Figure 1, Item 10).
2. Connect positive end of 9-volt battery (Figure 2, Item 1) to pin 86 on relay (Figure 2, Item 2).
3. Connect negative end of 9-volt battery (Figure 2, Item 3) to pin 85 on relay (Figure 2, Item 4).
4. Listen for an audible click indicating coil has energized.
If audible click is not heard, coil is bad. Replace relay.
5. If audible click is heard, check for continuity between pin 30 (Figure 2, Item 5) and pin 87a (Figure 2, Item 6) on
relay.
If there is continuity, relay is good. Reinstall relay.
If there is no continuity, relay is defective. Replace relay.
Figure 2. MPC Box Relay Test.