Diagnostic System Check - VDOT

VDOT A/C System Diagnosis (Part 1 Of 3):

VDOT A/C System Diagnosis (Part 2 Of 3):

VDOT A/C System Diagnosis (Part 3 Of 3):

VDOT A/C System Diagnosis

Use the following procedures to diagnose insufficient cooling for the V5 compressor and the VDOT refrigeration systems.

Use these procedures in conjunction with an appropriate service manual information.

The V5 compressor is a variable displacement compressor which matches air conditioning demand by changing the stroke rather than cycling the clutch. A control valve is located in the rear head of the compressor. The control valve senses the compressor low side pressure and causes the compressor mechanism to change stroke. Because the V5 compressor always runs and the system does not cycle, these diagnostic procedures differ from those used for fixed displacement systems. Use these procedures in order to avoid needlessly replacing A/C components.

Due to the variable displacement feature, special caution is necessary when diagnosing insufficient cooling conditions with the V5 compressor. During extended periods of shutdown, liquid refrigerant collects in the compressor crankcase. This is normal. The cooling action may be delayed for up to 2 minutes until the refrigerant is pumped from the compressor crankcase.

Certain conditions which are normal to proper air conditioning system operation may lead an owner to wrongly suspect a problem.

The air discharged from the air conditioning system may not feel as cold as expected under conditions of high humidity. The reason is that the vaporized moisture in humid air heats more effectively than dry air does, making the humid air harder to cool.

In terms of overall comfort, however, the dryer dehumidified air coming from the air conditioning system during hot, humid weather evaporates more moisture on a person's skin, providing more of a cooling effect than might be felt from cooler but more humid air.

This fact should be explained to an owner if no mechanical cause is found for a persistent complaint of insufficient cooling.