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Detecting leaks in the refrigerant gas loop > < Verification for vehicles with butterfly (throttle), collection tank and regulating valve for the air conditioning compressor N

Polo Mk4

Nominal values
Nominal values
High pressure side:
Gradual rise from outlet pressure (at the time of connecting the pressure gauge) up to a maximum pressure of 20 bar.
Low pressure side:
   
Gradual fall of the outlet pressure (at the time of connecting the pressure gauge) to the value given in the diagram.
A - Low pressure (measured at the service terminal), expressed in absolute pressure bar.
B - Control current of the Adjustment valve for the air conditioning compressor -N280-.
C - Admissible tolerance limit.
  Note
t  The pressure in the high pressure side may, under adverse circumstances (extremely high ambient temperature and humidity), rise to almost 29 bar.
t  Control current -B- is shown in the measurement values block.
t  The high pressure measured by the High pressure sensor -G65- is indicated in the measurement values block → Vehicle diagnosis, testing and information system VAS 5051.
t  The low pressure is automatically adjusted to a value within the tolerance limits, based on the control current of the Adjustment valve for the air conditioning compressor -N280-, within the power limits of the compressor.
t  Under adverse conditions (extremely high ambient temperature and humidity), compressor power may not always be sufficient to reach the given value.
t  The effective nominal current of the adjustment valve must be greater than 0.3 A to ensure its correct activation.
t  For maximum cooling power, the control current is adjusted to values between 0.65 and 0.8 A (it varies from vehicle to vehicle and is indicated in the measurement values block).
t  When pressure is expressed as absolute pressure, 0 (zero) bar corresponds to an absolute vacuum. Normal atmospheric pressure is equal to 1 (one) bar of absolute pressure. On most pressure gauge scales, 0 (zero) bar equals 1 (one) bar of absolute pressure (identifiable by the indication (–1) below the (0)).
  A87-0377
Admissible deviation from the nominal valuePossible cause of the faultTroubleshooting
l  High pressure remains constant or rises only marginally (above the value measured with the engine stopped).
l  Low pressure decreases rapidly to the value given in the diagram or below it.
l  The desired cooling power is not reached.
t  Activation of the Adjustment valve for the damaged air conditioning compressor -N280-.
t  The amount of refrigerant gas in the loop is too small.
–  Check operation of the Adjustment valve for the air conditioning compressor -N280-.
–  Suck refrigerant gas from the loop → Chapter.
l  The quantity of refrigerant gas sucked is significantly less than the filling capacity indicated.
–  Locate and eliminate the leak → Chapter.
–  Refill the refrigerant gas loop → Chapter.
l  High pressure is normal.
l  Low pressure matches the value given in the diagram.
l  The desired cooling power is not reached.
  
l  High pressure is normal.
l  Low pressure is very low (see diagram).
l  The desired cooling power is not reached.
t  The amount of refrigerant gas in the loop is too small.
–  Suck refrigerant gas from the loop → Chapter.
l  The quantity of refrigerant gas removed is significantly less than the filling capacity indicated.
–  Locate and eliminate the leak → Chapter.
–  Refill the refrigerant gas loop → Chapter.
–  Check again.

  Note
If no fault is found, vent the refrigerant gas loop → Chapter.
   
Admissible deviation from the nominal valuePossible cause of the faultTroubleshooting
l  High pressure rises only marginally above the value measured with the engine stopped.
l  Low pressure decreases only marginally.
l  The desired cooling power is not reached.
t  Activation of the Adjustment valve for the damaged air conditioning compressor -N280-.
–  Check activation of the Adjustment valve for the air conditioning compressor -N280-.
 
t  The air conditioning compressor is damaged.
–  Replace the air conditioning compressor.
l  High pressure rises above the nominal value.
l  Low pressure decreases only marginally.
l  The desired cooling power is not reached.
t  Bottle neck or obstruction in the refrigerant gas loop.
–  Check manually whether the refrigerant gas has temperature gradients.
l  A temperature gradient was detected in one of the components:
–  Replace the component if one of its rigid or flexible lines is either folded or bottle necked.
–  In case of obstruction, vent the refrigerant gas loop → Chapter.
–  Refill the refrigerant gas loop → Chapter.
–  Check again.
l  No fault was detected:
l  High and low pressure show normal values initially.
l  After some time, the high pressure rises above the nominal values.
l  The low pressure decreases rapidly to the values given in the diagram or below them.
l  The desired cooling power is not reached.
t  Humidity in the refrigerant gas loop.
–  Vent the refrigerant gas loop → Chapter.
–  Replace the collection tank.
–  Recheck in case of malfunction.
–  Refill the refrigerant gas loop → Chapter.
–  Check again.
l  High pressure is normal.
l  Low pressure is very low (see diagram).
l  The desired cooling power is not reached.
t  Activation of the Adjustment valve for the damaged air conditioning compressor -N280-.
–  Check activation of the Adjustment valve for the air conditioning compressor -N280-.
 
t  The air conditioning compressor is damaged.
–  Replace the air conditioning compressor.

  Note
t  If a fault is detected “with high pressure normal, low pressure very low”, please observe the following:
t  With this fault, the evaporator may freeze even though there is an adequate amount of refrigerant gas present in the refrigerant gas loop.
t  Check measurement values for the Air outlet temperature sensor for the evaporator -G263-.
t  Check activation of the Adjustment valve for the air conditioning compressor -N280-.
   
Admissible deviation from the nominal valuePossible cause of the faultTroubleshooting
l  High pressure is normal or very high.
l  Low pressure is very high (see diagram).
l  The air conditioning compressor is noisy (especially after starting).
l  The desired cooling power is not reached.
t  There is excess refrigerant gas in the loop.
–  Suck the refrigerant gas from the loop → Chapter.
l  The quantity of refrigerant gas removed more or less matches the filling capacity indicated:
–  Replace the air conditioning compressor.
l  The quantity of refrigerant gas removed is significantly greater than the filling capacity indicated.
–  Refill the refrigerant gas loop → Chapter.
–  Check again.
l  High and low pressure show normal values initially.
l  The air conditioning compressor is noisy (especially after starting).
l  The desired cooling power is not reached.
t  There is excess refrigerant gas oil in the loop.
–  Suck the refrigerant gas from the loop → Chapter.
–  Refill the refrigerant gas loop → Chapter.

  Note
Excessive filling of refrigerant gas oil may occur, for example, when the compressor is replaced without correcting the amount of refrigerant gas oil.
   

Detecting leaks in the refrigerant gas loop > < Verification for vehicles with butterfly (throttle), collection tank and regulating valve for the air conditioning compressor N