The rain sensor is built into a housing which is mounted behind the rear view mirror on the windshield.
The photodiode emits an infrared light beam of known intensity; the emitted light passes through the lens and is reflected by the windshield.
The reflected light beam enters back through the lens and then reaches the photodiode. The corresponding value taken without moisture on the windshield is used as the reference value for the automatic calibration process.
Subsequent deviations from this value cause the windshield wipers to be switched on.
If rain lands on the windshield then the light reflected by the windshield has a lower intensity. This loss of intensity is registered by the photodiode and, proportionally to the loss of intensity, the module switches on the windshield wipers with the required wipe speed (in intermittent or continuous mode).
When the automatic windshield wipers are switched on (wiper switch set to intermittent mode) the rain sensor is switched on and performs an automatic calibration according to the current conditions at the windshield.
To perform the automatic calibration, the windshield wipers perform a single wipe regardless of whether the windshield is wet or dry.
If the windshield remains dry after this wipe then the windshield wipers stop until moisture is registered on the windshield above the sensor.
On vehicles built from 12/2005, automatic calibration only takes place if the wiper switch was not set to the rain sensing function before the ignition was switched on.
The sensitivity of the rain sensor can be changed by adjusting the control resistor for the intermittent mode of the windshield wipers.
- Adjusting ring position 1: high sensitivity
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The wipers wipe even if only a small amount of water has been measured on the windshield.
- Adjusting ring position 6: low sensitivity:
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The wipers only wipe if a large amount of water has been measured on the windshield.
Windshield wash/wipe system
Wiper functions
The windshield wash/wipe system will only operate if the ignition switch is in the position "I" or "II".
Five wash functions are available: "Off", "Flick-wipe", "Speed 1", "Speed 2" and "Intermittent" or "Automatic wipe" (depending on the vehicle specification).
In "Speed 1" or "Speed 2" mode, the wipers are operating continuously at either normal speed or fast speed.
When the intermittent wipe mode is switched on the windshield wipers operate at normal speed with the following wiper delays:
- Wiper delay 1: 1 second
- Wiper delay 2: 3.5 seconds
- Wiper delay 3: 6 seconds
- Wiper delay 4: 9.5 seconds
- Wiper delay 5: 15.5 seconds
- Wiper delay 6: 22 seconds
NOTE:In the event of a failure, or if the control resistor is not connected the default time for the wiper delay is 8 seconds.
When the windshield washer switch is operated washer fluid is sprayed onto the windshield. After a short delay designed to protect the wiper blades the wipers perform 2 or 3 wipes at low speed.
If when the windshield washer switch is activated the windshield wipers are switched off, then a single wipe is performed 4 seconds after the wipers have returned to the home position after performing the 2 or 3 wipes.
If when the windshield washer switch is activated the wipers are in intermittent mode, and if the selected wiper delay time is longer than 6 seconds, then a single wipe is performed 6 seconds after the wipers have returned to the home position after performing the 2 or 3 wipes. If the selected delay time is less than 6 seconds then no post wipe is required.
The post wipe function on the windshield ensures that any water remaining on the windshield after washing is wiped away. It is only required if the wipers are switched off or they are set to intermittent mode.
Automatic wiper function
In vehicles built from 12/2005 without rain sensor, a speed-dependent wiper function is implemented in the GEM on the mid and high-end equipment versions.
When the windshield wipers are switched on, the GEM reduces the wiper speed by one setting if the vehicle is driven at walking speed or comes to a standstill.
When the vehicle speed is increased, the wiper speed automatically returns to the previous setting.
If the wiper lever is actuated during automatic function, the automatic wiper function is switched off and the wiper speed corresponds to the newly-selected setting.
Rear window wash/wipe system
The rear window wash/wipe system will only operate if the ignition switch is in the position "II".
The GEM changes the wiper delay time of the rear window wiper according to the switch setting of the windshield wipers.
If the wiper switch is in the "OFF" position, or in "intermittent" mode or the "automatic wipe" setting (no wiping or low speed wiping), then the wiper delay time for the rear window is 10 seconds.
If the wiper switch is in the "normal speed" position, "fast speed" position or the "automatic wipe" setting (high speed wiping), then the wiper delay time for the rear window is 6 seconds.
If the switch for the rear window washer is pressed, then washer fluid is sprayed onto the rear window, and the wiper operates continuously at low speed. When the switch is released the rear window wiper performs another 2-3 wipes.
If the switch for the rear window washer fails while switched ON, or if it is continuously operated for more than 60 seconds, then the switch signal is ignored by the GEM, the wiper returns to the park position and a trouble code is stored for the switch.
If reverse gear is engaged and the windshield wiper switch is in the normal, high speed or automatic windshield wiper (wiping at high speed) position, the rear window wiper operates continuously until the gearshift lever is moved back to the neutral position.
If reverse gear is engaged and the windshield wiper switch is in the "intermittent mode" or "automatic windshield wiper" (no wiping or low speed) position, then the rear window wiper follows the movement of the windshield wipers. When the wipers leave the park position the rear window wiper also performs a wipe.
Headlamp washer system
CAUTION:Do not operate the headlamp washer system for more than 10 seconds, and never with an empty fluid reservoir.
The headlamp washer system operates when the windshield washers are actuated if, at the same time, the light switch is set to "low beam" or if the "autolamp" function has switched on the headlamps. The system is controlled electrically by the headlamp washer relay, which is actuated by the GEM.
In order to prevent excessive washer water consumption in vehicles built from 12/2005, the headlamp washer system is only activated on every fourth actuation of the windshield washer switch, provide that 10 minutes have not elapsed since the first actuation of the headlamp washer system. If the windshield washer switch is actuated again after 10 minutes, the headlamp washer system is activated and the timer is restarted.
Overview
