TM 9-2320-280-34
Table 2-3. Air Conditioning Troubleshooting (Cont'd)
MALFUNCTION
TEST OR INSPECTION
AIR-CONDITIONER COMPRESSOR
NOTE
Before beginning compressor troubleshooting or inspection procedures, always
clean away oil, grease, dirt, and refrigerant residue.
3. INSUFFICIENT COOLING
a. If Air-Conditioner Compressor Runs Smoothly, Perform the Following:
Step 1. Connect manifold gauge set to low and high service connector ports (para. 14-17 or 14-27.1).
Step 2.
Run compressor at idle speed (6.2 L at 650 rpm, 6.5 L at 700 rpm) for five minutes.
Step 3.
If unusually high low pressure is observed in combination with unusually low high side pressure, stop
compressor and measure elapsed time that high side pressure is equal to low side pressure. If less than two
minutes, then the reed valve or head gasket may be defective. Disassemble and replace components
NOTE
During disassembly, check for head gasket damage, a broken or deformed reed
valve, dirt, or other foreign material stuck under reed valve or gasket, valve
plate damage, cracks, etc.
Step 4.
If unusually low side pressure and high side pressure are observed, check for low refrigerant charge or
refrigerant leaks and replenish refrigerant as necessary (para. 14-17 or 14-27.1).
Step 5.
Check compressor for oil leak under seal area between shaft and compressor. Replace shaft seal if defective
(para. 14-27 or 14-27.11).
Step 6.
Check for damaged front housing O-ring (missing or protruding sections). Replace O-ring, if damaged
(para. 14-27 or 14-27.11).
Step 7.
Check for oil around cylinder head. Inspect gasket, service port and fittings for looseness and damage.
Tighten loose fittings and replace defective gaskets or other defective parts (para. 14-27 or 14-27.11).
Step 8.
Check for oil seepage from filler hole. Inspect O-ring and plug for damage. Replace defective components
(para. 14-27 or 14-27.11).
Step 9.
Check for oil seepage from cracks in cylinder block. Replace compressor if cracks are found
(para. 14-24 or 14-27.8).
b. If Air-Conditioner Compressor Runs Intermittently or is Inoperative, Perform the Following:
Step 1. Check belt tension. Restore belt tension (TM 9-2320-280-20).
Step 2.
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
Step 1. Inspect field clutch lead wire. If wire is broken or damaged, replace field coil (para. 14-27 or 14-27.11).
Step 2.
Disconnect leads 436 and 798 from field coil leads.
Step 3.
Connect positive lead of multimeter to circuit no. 436 on field coil. Connect negative lead of multimeter to
circuit no. 798 on field coil. Field coil should read 12.0 to 15.0 ohms resistance at 73.4F (23C). If field
resistance test is not within specifications, replace field coil (para. 14-27 or 14-27.11).
Step 4.
Connect leads 436 and 798 to field oil leads.
Step 5.
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).
d. If Compressor Runs Roughly, Perform the Following:
Step 1. Discharge air-conditioning system (para. 14-17 or 14-27.1).
Step 2.
Disconnect leads 436 and 798 from field coil and remove service valves (para. 14-25 or 14-27.9).
Step 3.
Rotate compressor shaft clockwise (facing compressor) using 3/4 in. socket and wrench on shaft nut.
Step 4.
Check for severe rough spots or catches while rotating shaft nut. If rough spots or catches are observed,
replace compressor (para. 14-24 or 14-27.8).
END OF TESTING!
Change 2
