TM 9-2320-280-34
Table 2-3. Air Conditioning Troubleshooting (Cont'd)
MALFUNCTION
TEST OR INSPECTION
4. UNUSUAL NOISE WITH CLUTCH ENGAGED
a. Inspect Compressor Mounting Component
Step 1. Check for a loose belt. Restore tension (TM 9-2320-280-20).
Step 2.
Check for broken bracket or compressor mounting gear. Replace damaged components (para. 14-26
or 14-24 for R-12. Para 14-27.10 or 14-27.8 for R-134a).
Step 3.
Check for missing, broken, or loose bolts at compressor and engine mounting points. Replace damaged or
missing components.
NOTE
Ensure correct torque has been applied to mounting bolts.
Step 4.
Check for loose or wobbling compressor pulley, and for shaft nut torque and "bottoming". Repair or replace
damaged components (para. 14-27 or 14-27.11).
b. Inspect Engine Compartment
Step 1. Disconnect belt (TM 9-2320-280-20) and operate engine at idle to isolate engine noise from air-conditioner
compressor noise. If noise condition stops, continue to step 2. If noise condition still exists, refer to
mechanical troubleshooting (table 2-1).
Step 2.
Check for proper refrigerant charge (malfunction 1a). Low refrigerant charge can cause unusual noise.
Step 3.
Check clutch air gap (space between pulley and front clutch plate) (para. 14-27 or 14-27.11) with feeler
gauge. Gap must be within range of 0.016 - 0.031 in. (0.406 - 0.787 mm).
c. Check Clutch Bearing Operation
Step 1. Remove drivebelt (TM 9-2320-280-20).
Step 2.
Rotate pulley by hand and listen for bearing noise while feeling for hard spots. If noise or hard spots are
excessive, replace pulley and front clutch plate assembly or bearing (para. 14-27 or 14-27.11).
d. Check Oil Level
Insufficient amount of oil may cause compressor to be noisy. Restore oil to correct level (para. 14-17 or 14-27.1).
e. Check Internal Compressor
Perform malfunction 3d, steps 1 through 3, to determine an internal compressor failure. Replace compressor, if
necessary (para. 14-24 or 14-27.8).
f. Inspect Valve Plate
Step 1. Remove and inspect valve plate. If compressor makes a "clacking" sound at idle speed, check the high side
and low side valves for damage. Replace if necessary (para. 14-27 or 14-27.11).
Step 2.
Perform malfunction 3a, steps 1 through 3, to determine pressure balance test. If high side pressure does
not increase to a normal value at engine idle while the low side pressure remains high, the head gasket
may be damaged. Replace if necessary (para. 14-27 or 14-27.11).
Step 3.
Check for a broken discharge reed valve, retainer, or suction reed valve. Replace if necessary
(para. 14-27 or 14-27.11).
END OF TESTING!
2-25
