TM 9-4120-402-14
Table 4-3. UNIT TROUBLESHOOTING - continued
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
8. FAN MOTOR DOES NOT OPERATE.
WARNING
Disconnect input power before performing internal electrical troubleshooting.
Voltages used can be deadly.
CAUTION
Use disconnect switch (NOT POWER CABLE) to disconnect power to unit.
Damage to cable connector pins will result if cable is used.
Step 1. Using wiring diagram (figure 4-10), check electrical connectors P12 and J12, P10 and J10,
P11 and J11, and individual wires for tightness and continuity.
Tighten, repair, or replace as indicated.
Step 2. Check operation of motor controller.
Step 3. Check operation of fan motor.
Step 4. Check operation of MODE selector rotary switch.
9. EXCESSIVELY NOISY OPERATION.
CAUTION
A knocking or hammering noise is usually caused by liquid refrigerant in the compressor. This
can seriously damage or destroy the compressor.
NOTE
Be sure unit has been connected to input power at least four hours prior to operation.
Step 1. Listen for a knocking or hammering sound when the compressor starts.
Turn MODE selector rotaryswitch to OFF/RESET immediately. Notify supervisor.
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