Checking of heated rear window Z1 — AUDI

Checking of
heated rear window
Z1
Note
Situations preventing activation of the heated rear window (short circuit in connection to rear window, open circuit in power supply to front operating and display unit,
Climatronic control unit
J255
) are stored as faults in the front operating and display unit,
Climatronic control unit
J255
"Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
If the voltage measured at the
energy management control unit
J644
at terminal
„30“
drops below a value stored in the
energy management control unit
J644
, the rear window heating is completely deactivated at present (or the power is reduced) to relieve the load on the alternator (the electronics system of the front operating and display unit,
Climatronic control unit
J255
reduces the actuation duty cycle from 100% to 90....0%)
"Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
If the heated rear window has to be deactivated on account of undervoltage, the indicator lamp in the button for the heated rear window in the front operating and display unit,
Climatronic control unit
J255
remains on. However if deactivation lasts longer than approx. 150 s, the front operating and display unit,
Climatronic control unit
J255
switches off the indicator lamp.
The measured value block of the front operating and display unit,
Climatronic control unit
J255
shows that the heated rear window is being actuated or indicates why there is no actuation in spite of a corresponding request
"Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
Checking actuation of heated rear window operation is described in the air conditioner guided fault-finding
"Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
At ambient temperatures below 0 °C, the heated rear window remains switched on until the ignition is switched off (manual deactivation is possible at any time). If the temperature during a driving cycle rises above 0 °C, the heated rear window is deactivated on completion of the operating period stored in the front operating and display unit,
Climatronic control unit
J255
(approx. 10 minutes).
At ambient temperatures above 0 °C, the heated rear window is deactivated automatically on completion of the operating period stored in the front operating and display unit,
Climatronic control unit
J255
(approx. 10 minutes) by the front operating and display unit,
Climatronic control unit
J255
(on vehicles with standard glass, for example, the actuation time is governed by the encoding of the front operating and display unit,
Climatronic control unit
J255
)
"Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.