volkswagen Workshop Repair Guides

Volkswagen Workshop Service and Repair Manuals

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Checking systems with an expansion valve, receiver and air conditioner compressor regulating valveN280 (with externally regulate > < Checking systems with a restrictor and reservoir and air conditioner compressor regulating valveN280 (with externally regulated

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Specifications:
Specifications:
High-pressure side:
Rising from starting pressure (when pressure gauge is connected) to 20 bar.
Low-pressure side:
   
Falling from starting pressure (when pressure gauge is connected) to diagram value.
A - Low pressure (measured at the service connection) in bar absolute pressure.
B - Control current for the air conditioner compressor regulating valve -N280-.
C - Permitted tolerance range.
  Note
t  Under unfavourable conditions (very high ambient temperatures, high atmospheric humidity), the pressure on the high-pressure side can increase to a maximum of 29 bar.
t  The control current -B- is indicated in the measured values block.
t  The high pressure is indicated in the measured values block → Rep. gr.87.
t  The low pressure is adjusted to within tolerances within the output range for the air conditioner compressor depending on the control current for the air conditioner compressor regulating valve -N280-.
t  Under unfavourable conditions (very high ambient temperatures, high atmospheric humidity), the output may be insufficient to achieve the specification in every case.
t  The set working current for the regulating valve must be greater than 0.3 A to ensure that the regulating valve is reliably activated.
t  At the setting for „maximum cooling power“, the control current should be approx. 0.8 A (indicated in the measured values block) → Rep. gr.87.
t  Absolute pressure means that 0 bar corresponds to an absolute vacuum. The normal ambient pressure corresponds to 1 bar absolute pressure. On most pressure gauges, a reading of 0 bar corresponds to an absolute pressure of one bar (which is confirmed by the existence of a -1 bar marking beneath the 0 scale marking).
  A87-0377
Possible deviation from specification Possible cause of faultRectifying fault
l  High pressure remains constant or increases only slightly (above the pressure measured when the engine is stopped),
l  Low pressure falls quickly to the diagram value or lower,
l  The required cooling output is not delivered.
t  Actuation of air conditioner compressor regulating valve -N280- is defective.
t  Insufficient refrigerant in circuit.
–  Check actuation of air conditioner compressor regulating valve -N280-.
–  Check for leaks using leak detector and rectify.
–  Recharge refrigerant circuit.
l  High pressure is normal,
l  Low pressure matches the diagram value,
l  The required cooling output is not delivered.
  
l  High pressure is normal,
l  Low pressure is too low (see diagram),
l  The required cooling output is not delivered.
l  High pressure is normal,
l  Low pressure is too low (see diagram),
l  The required cooling output is not delivered.
  

  Note
If no fault can be found for this complaint, purge (clean) refrigerant circuit with refrigerant R134a → Chapter. If this is not possible in your workshop, blow through refrigerant circuit with compressed air and dry with nitrogen → Chapter.
   
Possible deviation from specification Possible cause of faultRectifying fault
l  High pressure increases only slightly above the pressure measured when the engine is stopped,
l  Low pressure falls only slightly,
l  The required cooling output is not delivered.
t  Actuation of air conditioner compressor regulating valve -N280- is defective.
t  The air conditioner compressor is defective.
–  Check actuation of air conditioner compressor regulating valve -N280-.
–  Rinse (clean) refrigerant circuit → Chapter.
–  Renew air conditioner compressor.
l  High pressure rises above specification,
l  Low pressure falls only slightly,
l  The required cooling output is not delivered.
t  Restriction or obstruction in the refrigerant circuit.
–  Feel the refrigerant circuit with the hand to sense the temperature gradient.
l  At one component a temperature gradient will be detected:
–  If a hose or pipe is kinked or crushed, renew it.
–  In case of an obstruction, blow through refrigerant circuit with compressed air and nitrogen.
l  If no faults are found:
–  Rinse (clean) refrigerant circuit → Chapter.
l  High pressure and low pressure are normal at first, but after a while, the high pressure increases beyond the specification,
l  The low pressure falls to the diagram value or lower,
l  The cooling power called for is not delivered.
t  Moisture in the refrigerant circuit.
–  Blow through refrigerant circuit with compressed air and nitrogen.
–  Renew reservoir.
–  Repeat the check; if the system does not operate correctly
–  Rinse (clean) refrigerant circuit → Chapter.
–  Recharge refrigerant circuit.
–  Repeat check.
l  High pressure is normal,
l  Low pressure is too low (see diagram),
l  The cooling power required is delivered.
t  Actuation of air conditioner compressor regulating valve -N280- is defective.
t  The air conditioner compressor is defective.
–  Check actuation of air conditioner compressor regulating valve -N280-.
–  Rinse (clean) refrigerant circuit → Chapter.
–  Renew air conditioner compressor.

  Note
t  If the fault is „high pressure normal, low pressure too low “ note the following: if faulty the evaporator could ice up or the required cooling output is not delivered.
t  In this case, the evaporator may ice up although the correct quantity of refrigerant is present in the refrigerant circuit.
t  Check the measured value of the evaporator output temperature sender -G263- or evaporator temperature sensor -G308-.
t  Check the actuation of the air conditioner compressor regulating valve -N280-
→ Rep. gr.87
   
Possible deviation from specification Possible cause of faultRectifying fault
l  High pressure normal or too high,
l  Low pressure too high (see diagram),
l  The air conditioner compressor is noisy (especially immediately after being switched on),
l  The required cooling output is not delivered.
t  Too much refrigerant in circuit.
–  Extract some refrigerant from the refrigerant circuit.
l  The quantity of refrigerant extracted is about equal to the prescribed charge quantity:
–  Renew the air conditioner compressor.
l  The quantity of refrigerant extracted is significantly greater than the prescribed charge quantity:
–  Recharge refrigerant circuit.
–  Repeat check.
l  High-pressure and low-pressure are normal,
l  The required cooling output is not delivered.
t  Too much refrigerant oil in circuit.
–  Drain refrigerant circuit.
–  Rinse (clean) refrigerant circuit → Chapter.
l  High-pressure and low-pressure are normal,
l  The air conditioner compressor is noisy (especially immediately after being switched on),
l  The cooling power required is delivered.
  

  Note
t  Overfilling with refrigerant oil can occur if the refrigerant oil level was not checked after the air conditioner compressor was renewed.
t  If the air conditioner compressor is not to be replaced, drain refrigerant oil from air conditioner compressor via the drain plug. From the total amount of refrigerant oil, fill 50 g direct into air conditioner compressor and fill remainder in refrigerant circuit according to → vehicle-specific workshop manual.
   

Checking systems with an expansion valve, receiver and air conditioner compressor regulating valveN280 (with externally regulate > < Checking systems with a restrictor and reservoir and air conditioner compressor regulating valveN280 (with externally regulated