Specified Values

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High-Pressure Side:

Increasing from initial pressure (when connecting pressure gauges) to 20 bar (290 psi).

Low-Pressure Side:

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

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

A - Low pressure (measured at service connection) in bar absolute

B - Control current for A/C Compressor Regulator Valve -N280-.

C - Permissible tolerance range

NOTE:

Under unfavorable conditions (very high ambient temperatures, high humidity), pressure on high-pressure side may increase to max. 29 bar (421 psi).

The control current -B- is shown in the measured value block.

The high pressure is shown in the measured value block. Refer to the appropriate service information. .

Low pressure settles as a function of control current for A/C Compressor Regulator Valve -N280- within compressor output range in tolerance range.

Under unfavorable conditions (very high ambient temperatures, high humidity), compressor output may not always be sufficient to attain the specified value.

The specified operating current for the regulator valve must be greater than 0.3 A in order to ensure reliable valve activation.

In the setting "maximum cooling output" control current is regulated to approximately 0.8 A (displayed in measured value block). Refer to the appropriate service information. .

At absolute pressure, 0 bar corresponds to absolute vacuum. Normal ambient pressure corresponds to 1 bar absolute pressure. 0 pressure corresponds to an absolute pressure of one bar on most pressure gauges (indicated by -1 bar (14.5 psi) below 0).

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	Activation of A/C Compressor Regulator Valve -N280- is faulty. Not enough refrigerant in refrigerant circuit	-- Check activation of A/C Compressor Regulator Valve -N280-. -- Localize the leak with leak detector and eliminate-- 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 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 Required cooling output is not attained	Activation of A/C Compressor Regulator Valve -N280- is faulty. A/C compressor faulty.	-- Check activation of A/C Compressor Regulator Valve -N280-.-- Flush (clean) refrigerant circuit. Refer to REFRIGERANT CIRCUIT, FLUSHING WITH R134A REFRIGERANT .-- Replace A/C compressor.
High pressure increases above specification Low pressure drops only slightly 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 If no malfunction can be found: -- 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 reservoir.-- 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	Activation of A/C Compressor Regulator Valve -N280- is faulty. A/C compressor faulty.	-- Check activation of A/C Compressor Regulator Valve -N280-.-- Flush (clean) refrigerant circuit. Refer to REFRIGERANT CIRCUIT, FLUSHING WITH R134A REFRIGERANT .-- Replace A/C compressor.

NOTE:

For the malfunction "high pressure normal, low pressure too low", note the following: faulty, the evaporator can ice up or the cooling output is not reached.

With this malfunction, evaporator may ice up although quantity of refrigerant in circuit is OK.

Check measured values of Evaporator Vent Temperature Sensor -G263- or Evaporator Temperature Sensor -G308-.

Check the A/C Compressor Regulator Valve -N280- activation.

Refer to the appropriate service information .

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.
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

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.

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.