Checking of heated rear window -Z1 — AUDI

Notes:

If heated rear window cannot be switched on (on account of short circuit in connection to rear window, open circuit in power supply to -E87 (heating)), indicator lamp in button of -E87 (heating) lights when button is pressed and goes out again when released, however heating is not switched on.
If voltage measured by -E87 (heating) at terminal "30" drops below 12.5 V, heated rear window power is reduced to relieve load on alternator (-E87 (heating) electronics system reduces actuation duty cycle from 100% to 90....10%).

Special tools, testers and other items required

Vehicle diagnostic, testing and information system VAS 5051 (with current probe)
Adapter set V.A.G 1594 A

Test requirement:

All fuses OK

=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder

Switch off ignition.
Remove operating and display unit for air conditioner/Climatronic
-E87 (heating) => Page
80-21
.
Unplug connectors -D- and -F- from operating and display unit for air conditioner/Climatronic -E87 (heating).
Connect adapter cable V.A.G 1598/12 of test box to unplugged connector -D-.

Connect test box V.A.G 1598 A to adapter cable V.A.G 1598/12.

Measure voltage between contact 5 at connector -F- and socket 13 (earth connection) of test box.
Specification: approx. battery voltage

Measure resistance between contact 6 at connector -F- and socket 13 (earth connection) of test box.
Specification: Resistance approx. 0.5.....1.0 ω(ohms)

Notes:

As resistances of less than 10ωcannot be measured with sufficient accuracy using workshop equipment, it is not possible to determine a short circuit in the wiring or the heated rear window -Z1.
If resistance is too high, check for open circuit in wiring to heated rear window -Z1 and eliminate if necessary.

=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder

Attach connectors -D- and -F- to -E87 (heating). All connectors are then attached to -E87 (heating).
Guide wire to connector -F- contact "6" through 50 A current probe of VAS 5051/9.
Set VAS 5051 mode "Multimeter measurement: Current 50 A current probe".

Note:

All connectors at -E87 (heating) must be attached.

Start engine.
Switch on heated rear window at -E87 (heating). Lamp in button lights.
Specification: Reading switches from approx. 0 A to less than 25 A

Wait approx. 12 minutes.
Specification: Reading switches from less than 25 A to approx. 0 A (lamp in button goes out)

Notes:

Stray current may cause a low current reading on current probe with heated rear window switched off.
At ambient temperatures below 0 °C heated rear window remains on until ignition is switched off (manual switch-off of heater is possible at any time). If temperature rises above 0 °C in the course of a driving cycle, heated rear window is switched off on completion of operating period (approx. 12 minutes) stored in -E87 (heating).
At ambient temperatures of more than 0 °C heated rear window is switched off automatically by -E87 (heating) on completion of operating period (approx. 12 minutes) stored in -E87 (heating).