Volkswagen Polo Service & Repair Manual: Checking with Restrictor, Reservoir and A/C Compressor Regulator Valve
-N280-, Externally Regulated A/C Compressor
Note
Connecting service station. Refer to
→ Chapter „Connecting Service Station“. |
Observe test requirements. Refer to
→ Chapter „Pressures, Checking“. |
– |
Bring engine speed up to 2000 RPM. |
– |
Pay attention to the A/C service station pressure gauge. |
Note
Switching pressures for actuation of A/C Compressor
Regulator Valve -N280- and Coolant Fan -V7- are
vehicle-specific. |
Increasing from initial pressure (when connecting pressure
gauges) to 20 bar (290 psi). |
|
|
|
Decreasing from initial pressure (when connecting pressure
gauges) to the value in the graph. |
A - |
Low pressure (measured at service connection) in bar (psi)
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
→ Rep. Gr.87. |
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
→ Rep. Gr.87. |
At absolute pressure, 0 bar/psi corresponds to absolute
vacuum. Normal ambient pressure corresponds to 1 bar (14.5 psi)
absolute pressure. 0 bar/psi pressure corresponds to an absolute
pressure of 1 bar (14.5 psi) on most pressure gauges (indicated
by 1 bar (14.5 psi) below 0 bar/psi). |
|
|
|
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. |
|
Low pressure in line with value in graph |
Required cooling output is not attained |
|
|
|
Low pressure too low (see graph) |
Required cooling output is not attained |
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
→ Chapter „Refrigerant Circuit, Flushing (Cleaning) 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
→ Chapter „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. |
|
– |
Check activation of A/C Compressor Regulator Valve -N280-. |
– |
Flush (clean) refrigerant circuit. Refer to
→ Chapter „Refrigerant Circuit, Flushing (Cleaning) 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 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
→ Chapter „Refrigerant Circuit, Flushing (Cleaning) 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 |
|
– |
Flush refrigerant circuit with compressed air and nitrogen. |
– |
Repeat test if function is not OK. |
– |
Flush (clean) refrigerant circuit. Refer to
→ Chapter „Refrigerant Circuit, Flushing (Cleaning) with
Refrigerant R134a“. |
– |
Charge the refrigerant circuit. |
|
Low pressure too low (see graph) |
The required cooling performance is obtained |
|
Activation of A/C Compressor Regulator Valve -N280- is
faulty. |
|
– |
Check activation of A/C Compressor Regulator Valve -N280-. |
– |
Flush (clean) refrigerant circuit. Refer to
→ Chapter „Refrigerant Circuit, Flushing (Cleaning) with
Refrigerant R134a“. |
– |
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. |
|
|
|
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. |
|
High and low pressure normal |
Required cooling output is not attained |
|
To much refrigerant oil in the circuit. |
|
– |
Discharge the refrigerant circuit. |
– |
Flush (clean) refrigerant circuit. Refer to
→ Chapter „Refrigerant Circuit, Flushing (Cleaning) 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, 50 grams should be put in the A/C
compressor and the rest in the refrigerant circuit. Refer to
vehicle-specific repair manual. |
–
Turn off the ignition.
–
Connect pressure gauge battery (A/C service station).
–
Take pr ...
Specified Values
Note
Connecting service station. Refer to
→ Chapter „Connecting Service Station ...
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