TM-9-2320-280-34 HMMWV Direct Support & General Support Maintenance Manual Download
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TM 9-2320-280-34 Table 2-3. Air Conditioning Troubleshooting (Cont’d) MALFUNCTION TEST OR INSPECTION 28. TRANSMISSION NOISY AIR-CONDITIONER 1. INSUFFICIENT COOLING a. Check for Refrigerant Loss Step 1. Connect manifold gauge to low and high service connectors (para. 14-17). Step 2. Start vehicle engine and adjust speed to 1500 rpm (TM 9-2320-280-20). Step 3. Set thermostat switch and fan switch to maximum position (TM 9-2320-280-10). Step 4. Run vehicle with air-conditioner on for five minutes. Step 5. Check low side of manif old gauge for normal to low reading and high side for low reading (table 2-2). If these conditions occur, perform leak test, repair leaks, evacuate, and recharge as necessary (para. 14-17). b. Check for Air or Moisture in System Step 1. Perform malfunction 1a, steps 1 through 4. Step 2. Check low side of manifold gauge for normal to high reading (table 2-2). If sight glass has no bubbles, tiny bubbles, or occasional bubbles, discharge system, replace dryer bottle (para. 14-19), evacuate, and recharge system (para. 14-17). c. Check Expansion Valve Step 1. Perform malfunction 1a, steps 1 through 4. Step 2. Check high side of manifold gauge for high reading and low side for low reading (possible vacuum) (table 2- 2). If discharge (evaporator) air is cool, expansion valve sweating or frosted, or control tube loose, either reposition control tube or replace expansion valve (para. 14-21). NOTE If control tube must be repositioned, re-wrap bulb with insulating tape. Step 3. Check high side of manifold gauge for high reading and low side for high reading (table 2-2). If discharge (evaporator) air is warm, replace expansion valve (para. 14-21). d. Check Thermostatic Switch Step 1. Perform malfunction 1a, steps 1 through 4. Step 2. Check low and high side manifold gauge readings for normal reading (table 2-2). If system runs continuously, remains in on (evaporator freeze-up) or off (poor cooling) cycle, or is inoperative, but can be made operative by jumping battery to clutch power load wire, then relocate temperature sensor, perform electrical troubleshooting (TM 9-2320-280-20) or replace thermostat unit, as necessary (para. 14-15). e. Check Clutch Cycling Pressure Switch Step 1. Perform malfunction 1a, steps 1 through 4. Step 2. Check low side of manifold gauge for low reading and high side for normal reading (table 2-2). If clutch cycling system runs continuously, then the switch is stuck closed. Replace pressure switch (para 14-16). Step 3. Check low and high side of manifold gauge for an approximate 70 psi (483 kPa) reading. If system is inoperative, but can be made operative by jumping battery to clutch power lead wire, then the switch is stuck open. Replace pressure switch (para. 14-16). 2-22