TM 9-4120-360-14
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
Replace faulty mode selector switch.
Check continuity of electrical leads from relay (K5) terminals A2, B2, C2 and D2 to fan motor connector P9.
Step 5.
terminals D, E, H and G. If continuity is not shown in one or more leads. check from relay (K5) terminals A2, B2,
C2 and D2 to connector J3, terminals h, S, T and P to connector P9, terminals b, E, H and G If continuity is
shown in all these leads, motor is bad.
Replace open wire leads, or replace motor.
4. EVAPORATOR AIR OUTPUT VOLUME LOW
Inspect filters for dirt and clogging.
Step 1.
Clean and replace filters.
Inspect mist eliminator for dirt and clogging
Step 2.
Clean and replace mist eliminator
Check evaporator blower impeller for looseness, binding or damage.
Step 3.
Tighten setscrews or relieve binding as necessary, or replace damaged impeller.
Disconnect power from the air conditioner before doing maintenance work on the electrical
system. The voltage can be lethal.
Step 4.
Check wiring connections to fan motor, relay K5, and connector plugs for looseness.
Tighten loose connections.
5. EXCESSIVELY NOISY OPERATION
CAUTION
If knocking or hammering is heard when air conditioner is started up, shut down at once and report
the condition to direct support maintenance. The compressor maybe pumping liquid refrigerant,
which will cause severe damage.
Listen for knocking or hammering sounds. Install gauge set, and check for high discharge pressure.
Step 1.
Bleed off some refrigerant.
Step 2.
Check evaporator and condenser fan impellers for looseness, vibration or interference.
Tighten setscrews. Check impellers for damage which would cause out-of-balance condition, and
replace impeller and guard, shroud, etc.
Step 3.
Check fan and blower motor for wear, as indicated by noisy operation or excessive end-or side-play.
Replace bearings, or motor.
6. COMPRESSOR WILL NOT START
Check continuity of circuit breaker. Unscrew four panel fastener screws, and remove front access panel from air
Step 1.
conditioner. Unscrew four panel fastener screws, and remove junction box cover. Tag and disconnect leads from
circuit breaker, and check continuity of each pair of terminals. using an ohmmeter or continuity tester.
Replace circuit breaker if bad.
Step 2.
Check continuity of fuses.
NOTE
If a fuse indicates no continuity it may have blown because of a short circuit or overload in the
transformer or one of the other components. Using an ohmmeter or continuity tester, remove fuses
from fuse blocks and check continuity. Replace fuses that show no continuity, and proceed to
Step 3.
Step 3.
Check condition of high- and low-pressure cutout switches by pressing reset buttons.
Replace faulty pressure cutout switches.
4-10
