Automatic Interval Control (AIC)
AUTOMATIC INTERVAL CONTROL (AIC)Function
With the aid of a rain sensor, the automatic interval control (AIC) system senses water or dirt on the windshield and activates the windshield wipers accordingly.
The AIC consists of an optical element bonded on the windshield, to which an electronic evaluator is connected.
The system is active as of ignition lock position 1. The wiper/washer switch must be set to the first stage (intermittent wipe setting).
The wiper motor is activated by the general module of ZKE. The electronic evaluator sends the instruction to activate the wiper motor via the K-bus to the general module.
Optical element
The optical element is adhered to the windshield behind the rear-view mirror. It consists of a glass body (prism) which routes the beams emitted by infrared diodes at a defined angle to the windshield. The light beams reflected by the windshield are routed by the optical element to the infrared receivers.
The optical element is heated by a heating element to ensure condensation cannot form on it.
The optical element is bonded together with the windshield in a special process such as to guarantee the physical properties of the system. This bonding process cannot be carried out in the workshop. Therefore when replacing the windshield, a special windshield with the optical element already bonded to it must be used.
Electronic evaluator
The electronic evaluator is connected to the optical element by means of a catch mechanism.
It contains the electronic components as well as the infrared diodes and infrared receivers.
The instruction to activate the wiper motor is given via the K-bus interface.
Functional principle
Water on the windshield is detected on the basis of the reflection of infrared beams.
When the windscreen is dry, all of the beams sent out by the infrared diodes S that hit the windscreen with a defined angle are fully reflected by the windscreen and thus reach the infrared receiver E in full.
A proportion of these beams is deflected by a drop of water on the windshield (in the area of the infrared diodes). These beams no longer reach the infrared receiver E.
Depending on the amount of light in the infrared beams that reach the receiver, the degree of wetness (or soiling) is determined and, if applicable, a command is sent across the K bus to the general module BC1 to activate the wiper motor.
Operation
To switch on the automatic interval control, the wiper/washer switch must be moved up to the first stage (intermittent wipe) and the ignition lock must be switched to position 1 or 2.
The automatic interval control system then controls the wipe intervals. If the windshield is constantly wet (steady rain) the system activates continuous wiping in stage 1.
The wiper stage 2 can still only be set by way of the wiper switch (third stage).
Automatic interval control remains switched off if terminal R is switched off and on when the wiper switch is set to intermittent wipe. It is not activated before intermittent wipe mode is switched off and on.
Operating conditions
The following conditions are necessary to ensure trouble-free operation of the rain sensor:
The windshield must not be damaged (stone chips, scratches) or must not be heavily soiled (finger marks, streaks, wax film) in the area of the rain sensor.
The wiper blades must wipe the windshield dry without streaks.
To ensure trouble-free operation, the windshield should be cleaned regularly with a suitable wax-removing cleaning agent. The wiper blades should be replaced regularly.
Initialization
The reflection characteristics of the windshield depend on a large number of factors. In addition these characteristics also change as the windshield ages.
During the initial wipe cycles, a new electronic evaluator determines the degree of reflection of the windshield and stores this data in its non-volatile memory. From this point on, this data is constantly adapted to the windshield which is subject to a certain degree of aging over the course of time.
The stored adaptation values can be deleted with the diagnostic program (service functions). Renewed adaptation (initialization) to the windshield can then be carried out.
The initialization procedure is described in the program sequence.
Initialization is necessary:
After replacing the windshield
When a used electronic evaluator is installed in a vehicle