Checking With RESTRICTOR And Reservoir With Internally Regulated A/C Compressor

NOTE:

Connecting service station, refer to SERVICING STATION, CONNECTING FOR MEASURING AND TESTING .

Observe test requirements, refer to PRESSURES, CHECKING .

-- Bring engine speed up to 2000 RPM.

-- Check the pressure gauge on the A/C service station.

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 [For engine(s) BLV, CCTA, CBFA] Description and Operation .

Target values

High-pressure side

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

Low-pressure side

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

Fig 1: Identifying Permissible Tolerance Range Graph

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

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

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

C - Permissible tolerance range

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

E - Permissible tolerance range

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 REFRIGERANT CIRCUIT, FLUSHING 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 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 REFRIGERANT CIRCUIT, FLUSHING 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 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 REFRIGERANT CIRCUIT, FLUSHING 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	-- Refrigerant Circuit, Flushing with Compressed Air and Nitrogen-- Replace fluid reservoir.-- Repeat test if function is not OK.-- Flush (clean) refrigerant circuit. Refer to REFRIGERANT CIRCUIT, FLUSHING WITH REFRIGERANT R134A .-- Charge the refrigerant circuit-- Repeat 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 REFRIGERANT CIRCUIT, FLUSHING 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	To much refrigerant in the circuit.	-- Extract refrigerant from refrigerant circuit If quantity of refrigerant extracted roughly corresponds to specified capacity: -- Replace A/C compressor. If quantity of refrigerant extracted is substantially greater than specified capacity: -- Charge the refrigerant circuit-- Repeat test

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

To much refrigerant in the circuit.

-- Extract refrigerant from refrigerant circuit

If quantity of refrigerant extracted roughly corresponds to specified capacity:

-- Replace A/C compressor.

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

-- Charge the refrigerant circuit-- Repeat 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 refrigerant circuit-- Flush (clean) refrigerant circuit. Refer to REFRIGERANT CIRCUIT, FLUSHING 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 Maintenance, Diagnosis , 50 grams should be put in the A/C compressor and the rest in the refrigerant circuit.