A/C Refrigerant System Pressures, Checking

A/C Refrigerant System Troubleshooting

A/C Refrigerant System Pressures, Checking

Check A/C refrigerant system pressures using these three tests:

1 - Air temperature drop from center instrument panel outlet (A/C system cooling performance)

2 - A/C system high pressure

3 - A/C system low pressure

The combined results of all three steps determine which part of the A/C system is causing the problem, see table.

Test Conditions

• A/C refrigerant system fully charged; discharge, evacuate and recharge system if necessary

• Condenser and radiator clean and free of obstructions (spray clean if necessary)

• Air distribution can be adjusted correctly using control knobs (all air distribution doors reach end positions)

• Wiring OK per wiring diagram

• Outside (ambient) air temperature between 20-30°C (68-86°F)

• Drive belts for A/C compressor and Generator in good condition and properly tensioned

Test 1 - Checking A/C Cooling Performance

- Start engine.

- Set temperature control to maximum "cold".

- Press "A/C" button and select second blower speed.

- Adjust air distribution to instrument panel outlets.

- Insert thermometer into center instrument panel outlet and raise engine speed to approximately 1500 RPM.

Specified result

With humidity normal and outside (ambient) temperature between 20-25°C (68-77°F), system is cooling satisfactorily if air temperature from center instrument panel vent drops below 10°C (50°F) within 1 minute.

For higher ambient temperatures and/or higher humidity, specified air temperature from center instrument panel vent can be slightly higher.

If specified reading is not obtained, perform tests 2 and 3, then compare results of all three tests => table.

Test 2 - A/C System High Pressure, Checking

- Connect high- and low-pressure hoses of refrigerant recovery/ recycling/recharging unit Kent-Moore ACR4 or equivalent, to high- and low-pressure service valves.

- Disconnect electrical connector from Coolant Fan.

- Start engine.

- Set temperature control to maximum "hot".

- Press "A/C" button and select highest blower speed.

- Adjust air distribution to footwell outlets.

- Raise engine speed to approximately 1500 RPM.

Specified result

System high pressure is normal if high-pressure gauge reads 232 psi (16 bar) within 30 seconds.

If specified reading is not obtained, also perform test 3 and compare results of all three tests => table.

Test 3 - A/C System Low Pressure, Checking

- Connect high- and low-pressure hoses of refrigerant recovery/recycling/recharging unit Kent-Moore ACR4, or equivalent, to high- and low-pressure service valves.

- Start engine.

- Set temperature control to maximum "cold".

- Press "A/C" button and select first blower speed.

- Adjust air distribution to instrument panel outlets.

- Raise engine speed to 1500 RPM.

Specified result

System low pressure is normal if low-pressure gauge reads 22-36 psi (1.5-2.5 bar) within 30 seconds.

If specified reading is not obtained, compare results of all three tests => table.