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Rain Sensor Function BMW 5 series E60/E61

Zke 3 Central Body Electronics - Overview - All Models ~400 words

Rain Sensor Function

The rain sensor is online as soon as it receives KLR operating power.

  1. When the windshield wiper stalk switch is placed in the intermittent position the GM signals the rain sensor control module via the K-Bus of the request for intermittent wiping and the position of the knurled wheel (sensitivity).
  2. As an acknowledgement, the rain sensor sends a command via the K Bus to activate the wiper motor. If more than 12 seconds pass before the GM receives the acknowledgement, the GM concludes the rain sensor has a defect and operates the intermittent wipe function as a system not equipped with a rain sensor. The wiper intermittent cycling is based solely on the knurled wheel setting.
  3. The rain sensor continuously monitors the windshield for rain accumulation and signals the GM to activate the wipers based on the knurled wheel position and how fast the rain accumulates on the windshield.
  4. The knurled wheel position signal (1 -4) via the K bus informs the rain sensor of the selected level of sensitivity. Position 1 (least sensitive) delays the wiper activation signal. Position 4 (most sensitive) sends the wiper activation signal to the GM sooner.
  5. When the wiper motor park contacts signal the GM of the wiper arm position, the signal is simultaneously sent to the rain sensor as an indication that the windshield has been cleared of water drops and causes the rain sensor to reset the sensitivity delay timer back to 0.
  6. If night time driving is detected via the integral photocell, the sensitivity to water droplets is increased causing a shorter delay than day time driving.
  7. Depending on the intensity of the rain the wipers will be operated continuously as if set in the normal wiper stalk switch position regardless of the knurled wheel setting. For this reason, the vehicle speed signal on the K bus is not utilized on rain sensor equipped wiper systems.
  8. If the ignition switch is turned off with the wiper switch in the intermittent position, the rain sensor will only become active after the ignition is switched back on and one of the following occurs: The stalk switch is moved from the intermittent position and then back, The knurled wheel setting is adjusted, Or the wash function is activated.

The reasoning behind this switching strategy is to have the driver make a conscious decision to activate the system themselves.