## Air Conditioning

#### A/C System Tests (cont'd)

21-100

Pressure Test

Test results | Related symptoms | Probable cause | Remedy
Discharge (high) pressure abnormally high | After stopping compressor, pressure drops to about 196 kPa (2.0 kgf/cm{sup 2}, 28 psi) quickly and then falls gradually. | Air in system | Discharge, evacuate (see page 21-94) and recharge with specified amount (see page 21-96).
No bubbles in sight glass when condenser is cooled by water | Excessive refrigerant in system | Discharge, evacuate and recharge with specified amount.
Reduced or no air flow through condenser |

- Clogged condenser or radiator fins
- Condenser or radiator fan not working properly

- Clean
- Check voltage and fan rpm.
- Check fan direction.

Line to condenser is excessively hot. | Restricted flow of refrigerant in system | Restricted lines
Discharge pressure abnormally low | Excessive bubbles in sight glass; condenser is not hot. | Insufficient refrigerant in system |

- Check for leak.
- Charge system.

High and low pressures are balanced soon after stopping compressor. Low side is higher than normal. |

- Faulty compressor discharge valve
- Faulty compressor seal

Replace the compressor.
Outlet of expansion valve is not frosted, low-pressure gauge indicates vacuum. |

- Faulty expansion valve
- Moisture in system

- Replace
- Discharge, evacuate and recharge with specified amount.

Suction (low) pressure abnormally low | Excessive bubbles in sight glass; condenser is not hot. | Insufficient refrigerant in system |

- Repair the leaks.
- Discharge, evacuate and recharge with specified amount.
- Charge as required.

Expansion valve is not frosted and low-pressure line is not cold. Low-pressure gauge indicates vacuum. |

- Frozen expansion valve (Moisture in system)
- Faulty expansion valve

- Discharge, evacuate and recharge with specified amount.
- Replace the expansion valve.

Discharge temperature is low and the air flow from vents is restricted. | Frozen evaporator | Run the fan with compressor off, then check evaporator temperature sensor.
Expansion valve is frosted. | Clogged expansion valve | Clean or replace.
Receiver/dryer outlet is cool and inlet is warm (should be warm during operation). | Clogged receiver/dryer | Replace
Suction pressure abnormally high | Low-pressure hose and check joint are cooler than the temperature around evaporator. | Expansion valve open too long | Repair or replace.
Suction pressure is lowered when condenser is cooled by water. | Excessive refrigerant in system | Discharge, evacuate and recharge with specified amount.
High and low-pressure are equalised as soon as the compressor is stopped and both gauges fluctuate while running. |

- Faulty gasket
- Faulty high-pressure valve
- Foreign particle stuck in high-pressure valve

Replace the compressor.
Suction and discharge pressures abnormally high | Reduced air flow through condenser. |

- Clogged condenser or radiator fins
- Condenser or radiator fan not working properly

- Clean
- Check voltage and fan rpm.
- Check fan direction.

No bubbles in sight glass when condenser is cooled by water | Excessive refrigerant in system | Discharge, evacuate and recharge with specified amount.
Suction and discharge pressure abnormally low | Low-pressure hose and metal end areas are cooler than evaporator. | Clogged or kinked low-pressure hose parts | Repair or replace.
Temperature around expansion valve is too low compared with that around receiver/dryer. | Clogged high-pressure line | Repair or replace.
Refrigerant leaks | Compressor clutch is dirty. | Compressor shaft seal leaking | Replace the compressor.
Compressor bolt(s) are dirty. | Leaking around bolt(s) | Tighten bolt(s) or replace compressor.
Compressor gasket is wet with oil. | Gasket leaking | Replace the compressor.