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TM5-4120-377-14
a. Removal
(1) Tag and disconnect wire leads.
(2) Using wrench, remove four lock nuts from relay.
(3) Remove relay.
b. Inspection
(1) Check for loose, corroded, missing, or broken terminal connections.
(2) Check relay for cracks, evidence of overheating, and other visible damage. Replace if damaged.
c. Test
(1) Use continuity tester or a multimeter set on the lowest OHMS scale to check continuity between
terminals A1 and A2, B1 and B2, and C1 and C2. All three contacts should be open. If there is continuity,
replace the relay.
(2) Check continuity between coil terminals X1 and X2. If there is no continuity, the coil is open. Replace
the relay.
(3) Apply external 24 volts dc power across terminals X1 and X2 and repeat continuity checks between
terminals A1 and A2, B1 and B2, and C1 and C2. All three contacts should be closed. If there is no continuity,
replace the relay.
(4) Remove the external 24 volts dc power source from coil terminals X1 and X2.
d. Installation
(1) Using wrench, secure relay with four lock nuts.
(2) See tags and wiring diagram (fig. 4-20) and connect wire leads.
(3) Remove tags.
Follow-on procedure: Install junction box cover and lower front panel. (See para 4-47.)
4-107
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