Audi A2 2001 - Page 185

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Note
♦ If high cooling output is needed (for example, the outside tem‐
perature is very high, the blower speed it set on high but the
engine RPMs are low), then the A/C compressor will not bring
the pressure on the low pressure side to the value specified in
the diagram -C- (for example, for a certain time after turning
on the A/C). Compressor is actuated with maximum specified
control current, however delivery volume is no longer sufficient
at this engine speed to reduce pressure on low-pressure side
to value in graph. To check the A/C compressor control under
these conditions, for example, the fresh air blower is controlled
only with approximately 40% of the maximum voltage, check
the pressures at a lower fresh air blower speed. Check using
Vehicle Diagnosis, Testing & Information System -VAS5051B-
(“OBD“ or “Guided Fault Finding for the A/C system“) and ⇒
Heating, Ventilation and Air Conditioning; Rep. Gr. 87 ; Diag‐
nosis and Testing (vehicle-specific repair manual).
♦ Under unfavorable conditions (very high ambient tempera‐
tures, high humidity), pressure on high-pressure side may
increase to maximum 29 bar.
♦ Control current -B- is displayed in measured value block of
Front A/C display control head -E87- , Climatronic Control
Module -J255- .
♦ High pressure measured by High Pressure Sensor -G65- or
A/C Pressure/temperature Sensor -G395- is displayed in
measured value block of Front A/C Control Head -E87- , Cli‐
matronic Control Module -J255- .
♦ Low pressure settles depending on control current for A/C
Compressor Regulator Valve -N280- and control characteris‐
tic of expansion valve within compressor output range in tol‐
erance range.
♦ Under unfavorable conditions (very high ambient tempera‐
tures, high humidity), compressor output may not always be
sufficient to attain the specified value.
♦ If compressor capacity utilization is greater than 90%, pres‐
sure on low-pressure side may be in excess of tolerance range
C shown in graph (compressor output no longer sufficient).
♦ The specified operating current for the A/C Compressor Reg‐
ulator Valve -N280- must be greater than 0.3 A in order to
ensure reliable regulator valve actuation.
♦ In “maximum cooling output“ setting, control current for A/C
Compressor Regulator Valve -N280- is regulated to approxi‐
mately 0.65 A (up to 0.85 A). This measured value is vehicle-
specific and displayed in measured value block.
♦ At absolute pressure, 0 bar corresponds to absolute vacuum.
Normal ambient pressure corresponds to 1 bar absolute pres‐
sure. On the scales of most pressure gauges, 0 bar corre‐
sponds to an absolute pressure of 1 bar (can be seen from -1
bar mark below 0). Check using Vehicle Diagnosis, Testing &
Information System -VAS5051B- (“OBD“ or “Guided Fault
Finding for the A/C System“) and ⇒ Heating, Ventilation and
Air Conditioning; Rep. Gr. 87 ; Diagnosis and Testing (vehicle-
specific repair manual).
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4. Diagnosis and Testing 181