Volkswagen Touran Service Manual: Checking with Restrictor and Reservoir, with Internally Regulated A/C Compressor

Volkswagen Touran Service Manual / Heating, Ventilation and Air Conditioning / Pressures, Checking / Checking with Restrictor and Reservoir, with Internally Regulated A/C Compressor

Note

Connecting service station. Refer to → Chapter "Connecting Service Station".

Observe test requirements. Refer to → Chapter "Pressures, Checking".

Bring engine speed up to 2000 RPM.

Pay attention to the A/C service station pressure gauge.

Note

Switching pressures for refrigerant circuit switches are vehicle-specific.

Connection with valve for low-pressure switch or at evaporator is only to be used for vehicles with no service connection on low-pressure side and inaccessible connection at compressor or accumulator (measurement accuracy). Only applies to certain vehicles.

Refer to → Rep. Gr.87.

Specified Values

High-pressure side:

Increasing from initial pressure (when connecting the pressure gauges) to a maximum of 20 bar (290 psi).

Low-pressure side:

Decreasing from initial pressure (when connecting pressure gauges) to the value in the graph.

A -	High pressure (measured at service connection) in bar (psi)

B -	Low pressure (measured at connection with valve at compressor or accumulator) in bar (psi).

C -	Permissible tolerance range

D -	Low pressure (measured at connection with valve for low-pressure switch or at service connection) in bar (psi)

E -	Permissible tolerance range

Checking with Restrictor and Reservoir, with Internally Regulated A/C Compressor

Possible deviation from specification

Possible cause of fault

Corrective action

High pressure remains constant or increases only slightly (above pressure with engine stopped),

Low pressure quickly drops to value in graph or below

Required cooling output is not attained

Not enough refrigerant in refrigerant circuit

Check for leaks and correct.

Charge the refrigerant circuit.

High pressure normal

Low pressure in line with value in graph

Required cooling output is not attained

High pressure normal

Low pressure too low (see graph)

Required cooling output is not attained

Note

If no malfunction is found with this complaint, flush (clean) refrigerant circuit with refrigerant R134a. Refer to → Chapter "Refrigerant Circuit, Flushing (Cleaning) with Refrigerant R134a". If that is not possible in this workshop, flush the refrigerant circuit with compressed air and remove moisture with nitrogen. Refer to → Chapter "Refrigerant Circuit, Flushing with Compressed Air and Nitrogen".

Possible deviation from specification

Possible cause of fault

Corrective action

High pressure only increases slightly above pressure with engine stopped

Low pressure drops only slightly

Required cooling output is not attained

A/C compressor faulty.

Flush (clean) refrigerant circuit. Refer to → Chapter "Refrigerant Circuit, Flushing (Cleaning) with Refrigerant R134a".

Replace A/C compressor.

Possible deviation from specification

Possible cause of fault

Corrective action

High pressure increases above specification

Low pressure quickly drops to value in graph or below

Required cooling output is not attained

Constriction or obstruction in refrigerant circuit

Run hand over refrigerant circuit to check for differences in temperature

If difference in temperature is found at one component:

Replace the hose or pipe if kinked or constricted.

In the event of an obstruction, flush refrigerant circuit with compressed air and nitrogen

Repeat test if function is not OK.

Flush (clean) refrigerant circuit. Refer to → Chapter "Refrigerant Circuit, Flushing (Cleaning) with Refrigerant R134a".

High and low pressure normal at first After some time,

high pressure increases above specification

Low pressure quickly drops to value in graph or below,

Required cooling output is no longer attained.

Moisture in refrigerant circuit

Flush refrigerant circuit with compressed air and nitrogen.

Replace receiver/dryer.

Repeat test if function is not OK.

Flush (clean) refrigerant circuit. Refer to → Chapter "Refrigerant Circuit, Flushing (Cleaning) with Refrigerant R134a".

Charge the refrigerant circuit.

Repeat the test.

High pressure normal

Low pressure too low (see graph)

The required cooling performance is obtained

A/C compressor faulty.

Flush (clean) refrigerant circuit. Refer to → Chapter "Refrigerant Circuit, Flushing (Cleaning) with Refrigerant R134a".

Replace A/C compressor.

Note

For the malfunction "high pressure normal, low pressure too low", note the following:

This fault may cause the evaporator to ice up or the A/C Refrigerant Low Pressure Switch -F73- to shut off the compressor although the amount of refrigerant in the circuit is OK.

Possible deviation from specification

Possible cause of fault

Corrective action

High pressure normal or too high

Low pressure too high (see graph)

A/C compressor noise (particularly after switch-on)

Required cooling output is not attained

Too much refrigerant in the circuit.

Extract refrigerant from the refrigerant circuit

If quantity of refrigerant extracted roughly corresponds to specified capacity:

Replace the A/C compressor.

If quantity of refrigerant extracted is substantially greater than specified capacity:

Charge the refrigerant circuit.

Repeat the test.

Possible deviation from specification

Possible cause of fault

Corrective action

High and low pressure normal

Required cooling output is not attained

To much refrigerant oil in the circuit.

Discharge the refrigerant circuit.

Flush (clean) refrigerant circuit. Refer to → Chapter "Refrigerant Circuit, Flushing (Cleaning) with Refrigerant R134a".

High and low pressure normal

A/C compressor noise (particularly after switch-on)

The required cooling performance is obtained

Note

Overfilling with refrigerant oil can occur in the event, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil.

If the A/C compressor is not replaced, the refrigerant oil should be drained from the A/C compressor via the oil drain plug. Out of the entire quantity of refrigerant oil, 50 grams should be put in the A/C compressor and the rest in the refrigerant circuit.

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