Heated Windshield
Heated Windshield
• Use of the optional "heated front windshield" is open.
Operation of heated Windshield
• The Heated Windshield Control Module (J505) - A - is installed in the right luggage compartment behind the luggage compartment lining - B -.
• The Heated Windshield Control Module (J505) - A - if present is activated by the Climatronic Control Module (J255) A/C control head via the A/C system"LIN Bus" data bus system (reads the measured value block) => Vehicle Diagnosis, Testing and Information System VAS 5051.
- After starting the cold engine, if outside temperature is less than + 5° C and "Auto" is set on the Climatronic Control Module (J255) A/C control head. The temperature on the Climatronic Control Module (J255) A/C control head has to be set such that the air conditioner is in heating mode and the Left Vent Temperature Sensor (G150), Right Vent Temperature Sensor (G151), and Center Vent Temperature Sensor (G191) do not record a temperature in excess of + 35°. Depending on the outside temperature, heating period is a maximum of 6 minutes (at -40°).
- When selecting the "defrost" operating mode on the Climatronic control module (J255) A/C control head if the 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.
• The Heated Windshield Control Module (J505) - A - activates the Heated Windshield (Z2) if the following basic conditions are met.
- The Climatronic control module (J255) A/C control head actuates the heated windshield control module (J505).
- Voltage at Heated Windshield Control Module (J505) is greater than 12.70 V.
- The Heated Windshield Control Module (J505) is not overheated
• The Climatronic Control Module (J255) A/C control head activates the Heated Windshield Control Module (J505) via the A/C system "Lin Bus" data bus system. If there is a condition in the Heated Windshield Control Module (J505) that prevents the heater from switching on, Climatronic Control Module (J255) A/C control head is informed via this data line that windshield heating is not switched on => Vehicle Diagnosis, Testing and Information System VAS 5051.
• Electrical resistance of metal foil in 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) converts the electrical system voltage for the Heated Windshield (Z2) 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 13.10 V, the Heated Windshield (Z2) will be actuated with a voltage of 41 V => Vehicle Diagnosis, Testing and Information System VAS 5051.
• To prevent electrical system overload, Heated Windshield Control Module (J505) regulates heating output of the Heated Windshield (Z2). 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 maximum 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 2.5 Ohm (open circuit or contact resistance), the Heated Windshield Control Module (J505) will not switch the windshield heating on or off => Vehicle Diagnosis, Testing and Information System VAS 5051.