Volkswagen Golf Service & Repair Manual: Checking systems with a restrictor and collector (with internally regulated
air conditioner compressor)
Note
Connecting air conditioner service station
→ Chapter. |
Observe the test prerequisites
→ Chapter. |
– |
Raise engine speed to 2,000 rpm. |
– |
Observe air conditioner service station pressure gauge. |
Note
Switch pressures for switches in refrigerant circuit are
vehicle-specific.
|
The connection with a valve for the low-pressure switch or
on the evaporator should only be used where the vehicle does not
have a service connection on the low-pressure side and access to
the connection on the air conditioner compressor or reservoir is
not possible (measurement accuracy). This only applies to
certain vehicles. |
|
|
|
Rising from starting pressure (when pressure gauge is
connected) to maximum 20 bar. |
|
|
|
Falling from starting pressure (when pressure gauge is
connected) to diagram value. |
A - |
High pressure (measured at the service connection) in bar
positive pressure. |
B - |
Low pressure (measured at the connection with the valve at
the air conditioner compressor or at the reservoir) in bar
positive pressure. |
C - |
Permitted tolerance range. |
D - |
Low pressure (measured at the connection with the valve for
the low-pressure switch or at the service connection) in bar
positive pressure. |
E - |
Permitted tolerance range. |
|
|
|
Possible deviation from specification |
Possible cause of fault |
Rectifying
fault |
High pressure remains constant or increases only slightly
(above the pressure measured when the engine is stopped), |
Low pressure falls quickly to the diagram value or lower,
|
The required cooling output is not delivered. |
|
Insufficient refrigerant in
circuit. |
– |
Look for leaks and rectify them. |
– |
Recharge refrigerant circuit. |
|
Low pressure matches the diagram value, |
The required cooling output is not delivered. |
|
|
|
Low pressure is too low (see diagram), |
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 fault |
Rectifying
fault |
High pressure increases only slightly above the pressure
measured when the engine is stopped, |
Low pressure falls only slightly, |
The required cooling output is not delivered. |
|
The air conditioner compressor
is defective. |
– |
Purge (clean) refrigerant circuit
→ Chapter. |
– |
Renew air conditioner compressor. |
|
Possible deviation from specification |
Possible cause of fault |
Rectifying
fault |
High pressure rises above specification, |
Low pressure falls quickly to the diagram value or lower, |
The required cooling output is not delivered. |
|
Restriction or
obstruction in the refrigerant circuit. |
– |
Feel the refrigerant circuit with the hand to sense the
temperature gradient. |
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. |
– |
Repeat the check; if the system does not operate correctly |
– |
Purge (clean) refrigerant circuit
→ Chapter. |
|
High pressure and low pressure are normal at first, but
after a time, |
The high pressure increases beyond the specified value, |
The low pressure falls to the diagram value or lower, |
The cooling power called for is not delivered. |
|
Moisture in the
refrigerant circuit. |
– |
Blow through refrigerant circuit with compressed air and
nitrogen. |
– |
Repeat the check; if the system does not operate correctly |
– |
Purge (clean) refrigerant circuit
→ Chapter. |
– |
Recharge refrigerant circuit. |
|
Low pressure is too low (see diagram), |
The cooling power required is delivered. |
|
The air conditioner compressor
is defective. |
– |
Purge (clean) refrigerant circuit
→ Chapter. |
– |
Renew air conditioner compressor. |
|
Note
If the fault is “high pressure normal, low pressure too low ” please
note the following: |
In this case, the evaporator may be iced up or the low-pressure
switch for air conditioning system -F73- has switched off the air
conditioning system compressor, although the correct quantity of
refrigerant is present in the refrigerant circuit. |
Possible deviation from specification |
Possible cause of fault |
Rectifying
fault |
High pressure normal or too high, |
Low pressure too high (see diagram), |
The air conditioner compressor is noisy (especially
immediately after being switched on), |
The required cooling output is not delivered. |
|
Too much refrigerant in
circuit. |
– |
Extract some refrigerant from the refrigerant circuit. |
The quantity of refrigerant extracted is about equal to the
prescribed charge quantity. |
– |
Renew the air conditioner compressor. |
The quantity of refrigerant extracted is significantly
greater than the prescribed charge quantity. |
– |
Recharge refrigerant circuit. |
|
Possible deviation from specification |
Possible cause of fault |
Rectifying
fault |
High-pressure and low-pressure are normal, |
The required cooling output is not delivered. |
|
Too much refrigerant oil in
circuit. |
– |
Drain refrigerant circuit. |
– |
Purge (clean) refrigerant circuit
→ Chapter. |
|
High-pressure and low-pressure are normal, |
The air conditioner compressor is noisy (especially
immediately after being switched on), |
The cooling power required is delivered. |
|
|
|
Note
Overfilling with refrigerant oil can occur if the refrigerant oil
level was not checked after the air conditioner compressor was renewed. |
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. |
Where vehicles have a restrictor and reservoir, check these
(with internally regulated air conditioning system compressor)
→ Chapter.
...
Note
Connecting air conditioner service station
→ Chapter.
Observe the test prerequisites
→ Cha ...
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