Refrigerant System Checks. Isuzu Isuzu MD Steel Tilt (F Model) 1998

For 1990-2009 cars only

Makes 🢒 Isuzu 🢒 1998 🢒 Isuzu MD Steel Tilt (F Model) 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Refrigerant System Checks

Table 1:	High Pressure Abnormally Low
Table 2:	Low Pressure is Abnormally High
Table 3:	Low Pressure is Abnormally Low
Table 4:	Low and High Pressures are Abnormally High
Table 5:	Low and High Pressures are Abnormally Low

High Pressure Abnormally Low

Problem	Action
The system contains insufficient refrigerant.	Check the refrigerant system for leaks. Refer to Leak Testing .
The expansion valve is clogged or defective, with a low pressure indicating vacuum.	Replace the expansion valve. Refer to Thermal Expansion Valve Replacement .
Frost or dew exists on the refrigerant line before and after the receiver/dryer or the dehydrator or the expansion valve and low pressure indicate vacuum. This may be due to restriction caused by debris or moisture in the receiver/dryer or dehydrator.	Replace the receiver/dryer or dehydrator. Refer to Receiver Dehydrator Replacement .
The high and low pressure balanced quickly with the engine shut off. This may be caused by a defective compressor seal or poor compressor operation.	Replace the compressor. Refer to Air Conditioning Compressor Replacement .

Low Pressure is Abnormally High

Problem	Action
The low pressure drops after the condenser is cooled by water. This may be caused by excessive refrigerant in the system.	Discharge the refrigerant. Recover the refrigerant. Recharge the refrigerant. Refer to Refrigerant Recovery and Recharging .
The low pressure hose temperature around the compressor refrigerant line connector is lower than around the evaporator. This may be caused by improper expansion valve operation.	Replace the expansion valve. Refer to Thermal Expansion Valve Replacement .
The high or low pressure balanced quickly with the engine off. This may be caused by improper compressor operation.	Replace the compressor. Refer to Air Conditioning Compressor Replacement .

Problem

Action

The low pressure drops after the condenser is cooled by water. This may be caused by excessive refrigerant in the system.

Discharge the refrigerant.
Recover the refrigerant.
Recharge the refrigerant.

Refer to Refrigerant Recovery and Recharging .

The low pressure hose temperature around the compressor refrigerant line connector is lower than around the evaporator. This may be caused by improper expansion valve operation.

Replace the expansion valve. Refer to Thermal Expansion Valve Replacement .

The high or low pressure balanced quickly with the engine off. This may be caused by improper compressor operation.

Replace the compressor. Refer to Air Conditioning Compressor Replacement .

Low Pressure is Abnormally Low

Problem	Action
The system contains insufficient refrigerant.	Check the refrigerant system for leaks. Refer to Leak Testing .
Frost on the expansion valve. This may be caused by a plugged expansion valve.	Replace the expansion valve. Refer to Thermal Expansion Valve Replacement .
A distinct temperature difference exists between the receiver/dryer or the dehydrator inlet and the outlet refrigerant lines. This may be caused by a clogged receiver/dryer or dehydrator.	Replace the receiver/dryer or dehydrator. Refer to Receiver Dehydrator Replacement .
The low pressure indicates that the vacuum and the expansion valve outlet refrigerant line is not cold. This may indicate that the expansion valve temperature sensor is defective.	Replace the expansion valve. Refer to Thermal Expansion Valve Replacement .
The low pressure reading decreases or shows a vacuum. This may be caused by a clogged or blocked refrigerant line.	Replace the refrigerant line.
The evaporator core is frozen. This may be caused by a defective A/C Temperature Sensor.	Replace the A/C Temperature Sensor. Refer to A/C Temperature Sensor in Heater/Vent Module Replacement .

Low and High Pressures are Abnormally High

Problem	Action
DEFINITION: The low and high pressure readings are abnormally high.
The system contains excessive refrigerant.	Discharge the refrigerant. Recover the refrigerant. Recharge the refrigerant. Refer to Refrigerant Recovery and Recharging .
The condenser is clogged or dirty.	Clean the condenser fins.
The system contains excessive air. This is indicated if the suction (low pressure) hose is not cold.	Discharge the refrigerant. Recover the refrigerant. Recharge the refrigerant. Refer to Refrigerant Recovery and Recharging .

Low and High Pressures are Abnormally Low

Problem	Action
The system contains excessive refrigerant.	Discharge the refrigerant. Recover the refrigerant. Recharge the refrigerant. Refer to Refrigerant Recovery and Recharging .