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This pattern appears on oscilloscope screen (for example on Ve‐
hicle diagnosis, testing and information system -VAS5051B- .)
when the following conditions are met.
– Ignition switched on (B+ at terminal 3 and Ground (GND) ter‐
minal 1 on high pressure sensor present)
– Making the adjustment on the oscilloscope: 5 volts/Division. =
(5 volts per unit DC voltage) 5 ms / Div. (5 milliseconds per
unit)
– Measuring lead (signal wire) connected to terminal 2 on high
pressure sensor.
– Measuring lead (shielding) connected to terminal 1 (Ground -
GND- on high pressure sensor).
Note
♦
The display shows a signal that is transferred when the pres‐
sure in the refrigerant circuit is approximately 7 bar, it corre‐
sponds to an approximate duty cycle of 25% (with compressor
not engaged, an ambient temperature of 30 °C and properly
filled refrigerant circuit).
♦
The impulse width -A- depends on the pressure in the refrig‐
erant circuit (if pressure increases, area -A- gets wider).
♦
The signal distance -B- is always 20 milliseconds (corre‐
sponds to frequency of 50 Hertz).
♦
The duty cycle is determined by the ratio of impulse width
-A- and signal distance -B-.
♦
Use the measuring leads form the Connector test set -V.A.G
1594/C- or an adapter lead for this test. To do this, for example,
use one connector each -A- and -B- (part number 1J0 973,703
and 1J0 973 803 and relevant terminal contacts), two standard
sockets for banana connectors -C- and three wires with 0.5
mm
2
diameter.
Audi TT 2007 ➤
Heating, Ventilation and Air Conditioning - Edition 01.2011
74
Rep. Gr.87 - Air Conditioning