TM 9-4120-388-14
Table 4-2. Unit Troubleshooting (Cont.)
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
9. FAN MOTOR (B2) DOES NOT OPERATE.
Disconnect Input power before performing internal electrical troubleshooting.
Voltages used can be deadly.
step 1. Using wiring diagram (Figure 4-16), 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.
step 2. Check operation of fan motor relay (K4).
step 3. Check operation of fan motor (B2).
Notify your supervisor if motor is defective.
step 4. Check operation of mode selector switch (S1).
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 refrig-
erant in compressor, which can seriously damage or destroy compressor. Notify
your supervisor.
11. EXCESSIVELY NOISY OPERATlON.
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 boss 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.