Select Service menu.

Activate the test mode by pressing the On/Off button in the right top corner of the Test display area until the value is On.

To test the operation of the heaters in the Heater test area:

To test the operation of the post-heater, press the On/Off button below the Post-heating text.

To test the operation of the defrosting resistor, first press the On/Off button below the Additional heating resistor text and then measure the output or observe the temperature of the defrosting resistor.