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.

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 R134A REFRIGERANT . If that is not possible in this workshop, flush the refrigerant circuit with compressed air and remove moisture with nitrogen. Refer to REFRIGERANT CIRCUIT, CLEANING 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 The requested cooling output is not attained.	A/C compressor faulty.	-- Flushing the refrigerant circuit. Refer to REFRIGERANT CIRCUIT, FLUSHING WITH R134A REFRIGERANT .-- Replacing the 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 REFRIGERANT CIRCUIT, FLUSHING WITH R134A REFRIGERANT .
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 REFRIGERANT CIRCUIT, FLUSHING WITH R134A REFRIGERANT .-- 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 REFRIGERANT CIRCUIT, FLUSHING WITH R134A REFRIGERANT .-- Replace the 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) The requested 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: -- Replacing 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 pressure normal or too high
Low pressure too high (see graph)
A/C compressor noise (particularly after switch-on)
The requested 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:

-- Replacing 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	Too much refrigerant oil in the circuit.	-- Discharge the refrigerant circuit.-- Flush (clean) refrigerant circuit. Refer to REFRIGERANT CIRCUIT, FLUSHING WITH R134A REFRIGERANT .
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 if, for example, the A/C compressor was 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 block connections. 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. Refer to the Vehicle-Specific Service Information.