After stopping the compressor, the pressure drops about 299 kPa (43 psi) quickly, then falls gradually.

Air is in the system.

Recover, evacuate, and recharge the system with the specified amount of refrigerant.

The condenser is excessively hot.

Excessive refrigerant is in the system.

Recover, evacuate, and recharge the system with the specified amount of refrigerant.

Reduced flow or no air flow through the condenser

The condenser or the radiator fins are clogged.

Clean the condenser or the radiator fins.

The condenser or the radiator fan is not working properly.

The line to the condenser is excessively hot.

A restricted flow of refrigerant is in the system.

Locate and repair the restriction.

The condenser is not hot.

Insufficient refrigerant is in the system.

High and low pressures are balanced soon after stopping the compressor.

A faulty compressor pressure relief valve is present.

Repair or replace the compressor.

Low side pressure is higher than normal.

A faulty compressor seal is present.

The outlet of the expansion valve is not frosted.

A faulty expansion valve is present.

Replace the expansion valve.

The low pressure gage indicates vacuum.

Moisture is in the system.

Recover, evacuate, and recharge the system.

The condenser is not hot.

Insufficient refrigerant is in the system.

The expansion valve is not frosted and the low pressure line is not cold.

A frozen expansion valve is present.

Replace the expansion valve.

The low pressure gage indicates a vacuum.

A faulty expansion valve is present.

The discharge temperature is low and the airflow from the vents is restricted.

The evaporator is frozen.

Clear the restricted evaporator case drain.

The expansion valve is frosted.

The expansion valve is clogged.

Clean or replace the expansion valve.

The receiver/dryer outlet is cool and the inlet is warm.

The receiver/dryer is clogged.

Replace the receiver/dryer.

The low-pressure hose and the check joint are cooler than the temperature around the evaporator.

The expansion valve is opened for too long.

Replace the expansion valve.

The capillary tube is loose.

Suction pressure is lowered when the condenser is cooled by water.

Excessive refrigerant is in the system.

Recover, evacuate, and recharge the system.

High and low pressure are equalized as soon as the compressor is stopped and both gages fluctuate while the compressor is running.

A faulty gasket is present.

Repair or replace the compressor.

A faulty high-pressure valve is present.

Foreign particles are stuck in the high-pressure valve.

Airflow through the condenser is reduced.

The condenser or the radiator fins are clogged.

Clean the condenser and the radiator.

The radiator cooling fans are not working properly.

The condenser is excessively hot.

Excessive refrigerant is in the system.

Recover, evacuate, and recharge the system.

The low-pressure hose and metal end areas are cooler than the evaporator.

The low-pressure hose is clogged or kinked.

Repair or replace the low-pressure hose.

The temperature around the expansion valve is low compared to the temperature around the receiver/dryer.

The high pressure line is clogged.

Repair or replace the high-pressure line.

The compressor clutch is dirty.

The compressor shaft seal is leaking.

Repair or replace the compressor.

The compressor bolts are dirty.

Leaking occurs around a compressor housing bolt.

Tighten the bolts or replace the compressor.

The compressor gasket is wet with oil.

The compressor gasket is leaking.

Repair or replace the compressor.