TM9-4120-401-14
4-41. HEATER RELAY (K1) AND DIODE (CR2). - continued
a. Inspect.
Check general condition of relay (1) and diode (2) and that terminals are not broken or missing. Replace if
damaged.
b. Test.
(1) Remove screw (3), lock washer (4), and flat washer (5).
(2) Push terminal post (6) away to access relay (1). Remove three sets of screws (7), lock washers (8), flat
washers (9), and Iii relay with bracket (10) as far as wire leads will allow.
NOTE
Terminal protective cover must be removed to access wire terminals.
(3) Tag and disconnect wire leads and diode (2) assembly from relay (1).
(4) Relay (1).
(a) Apply 28VDC to terminals X1 (positive) and X2 (negative).
(b) Using multimeter set to measure resistance, check continuity across terminals Al and A2, B1 and
B2, and Cl and C2. The multimeter must indicate that contacts are closed continuity).
Remove power. Multimeter must indicate that contacts are open (no continuity).
(c)
(d) Replace relay (1) if defective.
(5) Diode (2).
(a) Using a multimeter set to test diodes, connect black lead to band end of diode and red lead to
opposite end. The multimeter should indicate between 0.5 and 1.75 volt drop.
(b) Reverse the leads from step (a) above and check. The multimeter should give no indication.
(c) Replace diode (2) if defective.
(6) Connect wire leads and diode (2) assembly (band end to terminal X1) to relay (1) using wiring diagram
(7) Secure relay (1) and bracket (10) in unit using three sets of screws (7), lock washers (8), and flat
washers (9).
(8) Secure terminal post (6) to unit using screw (3), lock washer (4), and flat washer (5).
c. Replace.
(1) Remove screw (3), bck washer (4), and flat washer (5).
(2) Push terminal post (6) away to access relay (1). Remove three sets of screws (7), lock washers (8), flat
washers (9), and Iift relay with bracket (10) as far as wire leads will allow.
4-101
