TM-9-2320-280-34 HMMWV Direct Support & General Support Maintenance Manual Download
Page 52 of 1258
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). 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). 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 la). Low refrigerant charge can cause unusual noise. Step 3. Check clutch air gap (space between pulley and front clutch plate) (para. 14-27) 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 l isten 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). d. Check Oil Level Insufficient amount of oil may cause compressor to be noisy. Restore oil to correct level (para. 14-17). e. Check Internal Compressor Perform malfunction 3d, steps 1 through 3, to determine an internal compressor failure. Replace compressor, if necessary (para. 14-24). 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). 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). Step 3. Check for a broken discharge reed valve, retainer, or suction reed valve. Replace i f necessary (para. 14-27). END OF TESTING! 2-25