Checking with the temperature probe

Use the tip of the sensor to measure from the outside on the centre of the rear window.
The tip of the sensor must be positioned exactly on a heating wire on the rear window.

Fig 1: Checking Rear Window Heating With Temperature Probe
Courtesy of PORSCHE OF NORTH AMERICA, INC.
After switching the rear window heater on at room temperature, the temperature must increase by approximately 3°C within two minutes.
If no temperature increase is shown, the fault must be detected on the basis of the wiring diagram.