BMW i3 Active Cruise Control deactivated. Sensor dirty.

My 2017 i3 Active Cruise Control frequently drops out with the "Sensor dirty" error. The same thing happened on my 2014 i3. I think its related to condensation on the windshield glass in front of the camera. There are several forums that discuss the same problem. I also found a technical description of the camera heater. The heater is intended to prevent condensation. Much of the time I drive my i3, I am trying to conserve energy so I don't run the climate control. I think that's my mistake. I will now try to use this functional description to maximize the operation of the heater and see if that keeps my Active Cruise Control working better.

The full error message I get is: 'Active Cruise Control deactivated. Maintain safe distance. Sensor dirty. Please clean sensor, see Owner’s Manual.'

The mybmwi3.com forum has a thread about this topic as well as another thread at the speakev.com forum.

Another reference is this document, as well as this site.

The following functional description comes from a site called newtis.info. The Functional Description page is reproduced below. The linked page should be read to fully understand the description.

Camera-based driver support systems camera heating

The KAFAS camera heating (KAFAS = camera-based driver support systems) is located on the edge of the field of view of the KAFAS camera. The heating is intended to prevent the windscreen in front of the KAFAS camera from fogging over and freezing. This increases the availability of the camera-based driver support systems camera during cold weather.

Functional description

The KAFAS control unit controls the KAFAS camera heating. The camera-based driver support systems control unit evaluates the following input variables for the switch-on conditions and switch-off conditions of the KAFAS camera heating:

• Terminal status: Terminal 15 on
• Ambient temperature

  • The one-time heating duration depends on the ambient temperature.
  • Ambient temperature between 5 °C (41°F) and 15 °C (59°F): One-time heating duration e.g. 100 seconds
  • Ambient temperature below 5 °C (41°F): One-time heating duration e.g. 130 seconds
• Operation of the windscreen wiper
  • 
Windscreen wiper activated: Depending on the ambient temperature, the heating is periodically repeated (e.g. every 300 seconds) provided the precondition is present.
• Operation of the defrost button

• Defrost function activated: The one-time heating duration for the KAFAS camera heating depends on the ambient temperature.

• Defrost function deactivated: If the one-time heating duration for the KAFAS camera heating is not yet over and there is no other precondition, the heating is deactivated.
• Operation of the button for the heated rear window

• Heated rear window activated: The one-time heating duration for the KAFAS camera heating depends on the ambient temperature.

• Heated rear window deactivated: If the one-time heating duration for the KAFAS camera heating is not yet over and there is no other precondition, the heating is deactivated.
• Temperature and air humidity on inside of the windscreen

• The condensation sensor (constituent part of the rain-light-solar-condensation sensor) detects the temperature and the air humidity on the inside of the windscreen. Depending on the ambient temperature, the heating duration is periodically repeated provided the precondition is present (e.g. above 66% air humidity).
• Battery status