Audi TT Repair Manual page 78

Audi TT 2007 ➤
Heating, Ventilation and Air Conditioning - Edition 01.2011
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
2
mm diameter.
Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not
permitted unless authorised by AUDI AG. AUDI AG does not guarantee or accept any liability
with respect to the correctness of information in this document. Copyright by AUDI AG.
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Rep. Gr.87 - Air Conditioning