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Checking With RESTRICTOR, Reservoir And A/C Compressor Regulator Valve N280

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 actuation of A/C compressor regulator valve -N280- and radiator fan -V7- are vehicle-specific.

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 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
GWWA87-0377Courtesy 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.

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

The high pressure is shown in the measured value block. Refer to [For engine(s) BLV, CCTA, CBFA] Diagnosis and Testing .

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 [For engine(s) BLV, CCTA, CBFA] Diagnosis and Testing .

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 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 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 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
  • 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 REFRIGERANT R134A .-- 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 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 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 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
  • 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 REFRIGERANT R134A .-- Replace A/C compressor.
NOTE:

Note the following when the malfunction "high pressure normal, low pressure too low" is detected: faulty, the evaporator can ice up or the cooling output will not be 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 [For engine(s) BLV, CCTA, CBFA] Description and Operation

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
  • 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 if, 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.

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