Heated Glass Element: Description and Operation
Heated Windshield
• Heated Windshield Control Module (J505) - A - is installed in left luggage compartment beneath Battery (A).
• The Climatronic Control Module (J255) front A/C control head activate the Heated Windshield Control Module (J505) - A - => vehicle diagnosis, testing and information system VAS 5051 in the "Guided Fault Finding" function.
- After starting cold engine if outside temperature is less than + 5° C and "Auto" is set on front A/C control head, Climatronic Control Module (J255). Temperature must be set such on front A/C control head, Climatronic Control Module (J255) that air conditioner is in heating mode and temperature measured by sensors (Left Vent Temperature Sensor (G150), Right Vent Temperature Sensor (G151)) must not exceed + 35 °C. Depending on the outside temperature, heating period is a maximum of 6 minutes (at -40°).
- On selecting "Defrost" mode on front A/C control head, Climatronic Control Module (J255) if outside temperature is less than + 5° C. Depending on the exterior temperature, the heating period is between 2 and 6 minutes. As long as heated windshield is switched on, switch-on indicator lamp in Defrost button flashes. Actuation only takes place with engine running.
• Heated Windshield Control Module (J505) - A - switches on heated windshield if the following conditions are met.
- Front A/C control head, Climatronic Control Module (J255) actuates Heated Windshield Control Module (J505).
- Voltage at Heated Windshield Control Module (J505) is greater than 12.70 V.
- Heated Windshield Control Module (J505) is not overheated
• The Climatronic Control Module (J255) front A/C control head activates the Heated Windshield Control Module (J505) via a data line. If there is a condition in the Heated Windshield Control Module (J505) that prevents the heater from switch on, that information is transmitted to the Climatronic Control Module (J255) front A/C control head via the data line Vehicle diagnosis, testing and information system VAS 5051 in "Guided Fault Finding" function.
• The electrical resistance of the metal foil in - 1 - in the Heated Windshield (Z2) is approximately 1.9 Ohm. A voltage greater than the electrical system voltage is needed in order to reach the maximum possible heat output of approximately 1000 W (Watt) on the front window. The Heated Windshield Control Module (J505) for the Heated Windshield (Z2) converts the electrical system voltage into a variable voltage between 25 and 48 V, depending on the electrical system voltage. If the voltage at the Heated Windshield Control Module (J505) is greater than 13.10 V, the Heated Windshield (Z2) will be actuated with a voltage greater than 41 V up to a maximum of 48 V Vehicle diagnosis, testing and information system VAS 5051 in "Guided Fault Finding" function.
• To prevent electrical system overload, Heated Windshield Control Module (J505) regulates heating output of heated windshield. At vehicle voltage of 12.70 V, output is approximately 200 W and is gradually increased up to 1000 W at 13.10 volt. To prevent vehicle electrical system from collapsing when heated windshield is switched on, Heated Windshield Control Module (J505) allows for an output increase of 200 W per second.
• To prevent actuation of Heated Windshield (Z2) in the event of short circuit or open circuit in wiring, Heated Windshield Control Module (J505) checks resistance of Heated Windshield (Z2). If the measured resistance is less than 1.5 Ohm (short circuit) or greater than approximately 3.3 Ohm open circuit or contact resistance, the Heated Windshield Control Module (J505) will not switch the heating on or off vehicle diagnosis, testing and information system VAS 5051 in the "Guided Fault Finding" function.
• The Heated Windshield (Z2) is only activated in output diagnostic test mode up to a temperature of 40 °C in the vehicle interior. If the temperature is higher, "Function unknown" or " Functional currently unavailable" will be shown in the tester display Vehicle diagnosis, testing and information system VAS 5051 in "Guided Fault Finding" function.
• The switch-on function of the Heated Windshield Control Module (J505) can be checked with the Multimeter (V.A.G 1715) for example. Place the Multimeter (V.A.G 1715) current clamp over the Heated Windshield Control Module (J505) positive wire to the Heated Windshield (Z2) and select the "Measure current with current clamp" function on the Multimeter (V.A.G 1715). The display on the Multimeter (V.A.G 1715) changes from approximately 0 A to greater than 7 A.