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TM 5-4120-377-14
Table 4-2. TROUBLESHOOTING (Cont.)
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
9. FAN MOTOR (B2) DOES NOT OPERATE.
Step 1.
Step 2.
Step 3.
Step 4.
Disconnect input power before
Voltages used can be deadly.
performing internal electrical troubleshooting.
Using wiring diagram (fig. 4-20), check electrical connectors P3 and J3, P9 and J9, P12 and J12,
and individual wires for tightness and continuity.
Tighten, repair, or replace as indicated.
Check operation of fan motor relay (K4).
Test relay. (See para 4-57.) Replace relay if defective.
Check operation of fan motor (B2).
Test motor. (See para 4-63.) Contact direct support maintenance if motor is defective.
Check operation of mode selector switch (S1).
Test switch, (See para 4-40.) Replace switch if defective.
10. EXCESSIVE NOISE WHEN COMPRESSOR STARTS.
If a knocking or hammering sound is heard when compressor starts, turn mode
selector switch to OFF, immediately. Such noise is usually caused by liquid
refrigerant in compressor, which can seriously damage or destroy compressor.
Contact direct support maintenance.
11. EXCESSIVELY NOISY OPERATION.
Step 1. Isolate source of noise as near as possible, both by ear and touch.
Listen and feel at both front and back of cabinet.
Step 2. Check fans for looseness or damage, and for rotational clearance.
Tighten loose fans, adjust for rotational clearance, or replace fans. (See para 4-62 and 4-63.)
Step 3. Check all internal components for looseness, vibration, and security.
Tighten, adjust, and secure as necessary.
4-50
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