Electrically heated rear window and door mirrors
| Electrically heated rear window and door mirrors |
A number of heating wires are fastened to the inside of the rear window glass. On the 4D Saab 9-5 these heating wires also serve as an antenna for the audio system in combination with an antenna amplifier.
The glass in the door mirrors also has heating conductors.
On cars with MCC, the heating is turned on and off manually with a switch on the MCC panel which controls the relay via DICE.
On cars with ACC, the heating is turned on and off automatically by the ACC control module or manually by a switch on the ACC panel. The ACC control module then outputs a signal to the bus, which DICE uses to activate the heating relay. When DICE has activated the relay, it sends a message on the bus back to ACC, which lights the symbol on the display.
Normally, the electrical heating is on for 12 minutes or until it is turned off manually. DICE checks the battery voltage after 3, 6 and 9 minutes. If the voltage drops below 12.6V or rises above 16V, DICE turns off the heating.
To avoid putting a greater load on the battery than necessary when the starter motor is activated (+15 ON, +54 OFF), the DICE turns off the electric heating. When the ignition switch subsequently returns from START to ON, the DICE turns on the electric heating again. For reasons of safety, turn-off time is limited to 20 seconds so that electric heating will be functional even in the event of a fault, i.e. if no +54 current is present.
| Combined electrically heated rear window and antenna 4D |
The heating conductors in the rear window are also used as an antenna for the audio system in combination with an antenna amplifier.
The conductors in the rear window are grounded via an antenna filter (coil) to the car's bodywork. The resistance of the antenna filter (coil) is very low so there is no appreciable affect on the current flowing through it. The antenna filter (coil) is, however, a hinder to the high-frequency radio waves picked up by the conductors (antenna) and prevents them form grounding to the bodywork. There is a similar function built into the antenna amplifier that prevents radio waves from entering the car's wiring.
The antenna filter is located on the left-hand C pillar.
| Cars with MCC |
When the ignition is ON, +15 current is fed from fuse 26 to relay 113. If switch 504 is depressed, a voltage pulse is output to pin 18 on DICE 628 which grounds relay 113. +30 current is then fed from fuse 24 via the relay contacts and antenna amplifier 624 to the electrically heated rear window 115 which is grounded through the antenna filter 644.
Current is supplied at the same time to door mirrors 207D/P via fuse 18 and relay 113. The left-hand mirror is grounded at grounding point G33 and the right-hand one at grounding point G24.
| Cars with ACC |
When the ignition is ON, +15 current is fed from fuse 26 to relay 113. The ACC control module outputs a message on the bus to the DICE control module 628 when it requests activation (automatically or when the switch on the ACC panel is pressed). DICE then grounds the coil in relay 113 via pin 52. +30 current is then fed from fuse 24 via the relay contacts and the antenna amplifier 624 to the electrically heated rear window 115, which is grounded through the antenna filter 644.
Current is supplied at the same time to the heating elements in door mirrors 207D/P via fuse 18 and relay 113. The left-hand door mirror is grounded at grounding point G33 and the right-hand one at grounding point G24.
When the relay has been activated, DICE outputs a message on the bus to ACC which turns on the indicator light on its display.
| Electric heating uses the following information |
| Information | Sensor system | |
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Relay, activation
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DICE
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The relay turns on the heating.
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Relay, inactivation
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DICE
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The relay turns off the heating.
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