TM 9-4120-404-14
(1) Tag and disconnect all wires attached to heater relay.
(2) Remove four screws (1), four lock washers (2), and four flat washers (3).
(3) Remove heater relay (4) from unit.
b. Test.
(1) Using an ohmmeter set on lowest OHMS reading, check relay for continuity across terminals A1 and A2, B1
and B2, and C1 and C2.
(2) Each set of terminals should indicate an open circuit.
If any set of terminals indicate a closed circuit,
replace relay.
(3) Using ohmmeter set on lowest OHMS reading, check relay for continuity across terminals X2 and X1. Test
should indicate a closed circuit. If test indicates an open circuit, replace relay.
(4) Use an ohmmeter to test that diode (5) has an infinite resistance when tested. Reverse ohmmeter test
leads and check that diode now has continuity.
c. Installation.
(1) Place heater relay (4) into unit.
(2) Install four flat washers (3), four lock washers (2), and four screws (1).
(3) Refer to wire tags and reconnect wires to heater relay.
NOTE
When reconnecting diode to heater relay terminals X1 and X2, be sure to connect
"+" end of diode to terminal X1.
(4) Install front cover (see para. 3-27).
(5) Reconnect air conditioner to power source.
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