Dear Ask a Mechanic,
While driving my 2021 Nissan Rogue on Highway 401 through snow and slush, the sensor that is behind the Nissan logo on the grille had a slush build up which froze and caused one of the forward collision warnings to alert me it was not working. The sensors on the bumpers have also had slush freeze on them. As well, the LED headlights and running lights freeze because they do not generate enough heat. I now carry a spray bottle with a 70 per cent rubbing alcohol solution to clean the sensors and lights after driving in slushy conditions. Are you aware of this occurring with other vehicles with modern driving assistance sensors? – A slushy situation
Driving conditions are one of the major challenges facing engineers as they work toward building fully autonomous vehicles, many of which use high-resolution vision systems, like LIDAR, a laser-based optical technology that is very sensitive. It’s a major factor in why most real-world testing of these systems occurs in fair-weather locations, such as California and Arizona.
Even the less complex systems already available on the market – everything from adaptive cruise control and lane departure warnings to Level Two autonomy and the increasingly common collision mitigation systems – have issues with snow and slush build up. I’ve personally experienced this in a variety of different vehicles.
There are two primary types of sensors used in most of these systems: cameras and “millimetre wave” radar. Cameras are typically mounted near the inside top of the windshield, and benefit from being cleared by the wipers. Even so, ice accumulation in winter, heavy rainfall and even smeared bugs during the summer, can obscure the cameras enough to temporarily disable the system.
Radar sensors are normally mounted in the nose of the vehicle, either below the front bumper or, increasingly, hidden behind the badge in the grille. Because of the location, and a lack of heating in these areas, snow, ice, bugs and mud can all interfere with the sensors’ functions.
So far, the only vehicle that I’ve heard about that has a heater for its radar sensor is BMW’s new iX electric crossover. Regardless, cleaning the sensors and restarting the vehicle normally resets the system.
As you mention, it’s a similar situation with LED lights. I’m not aware of any factory LED lights that are heated, however several aftermarket headlight replacements do offer heated versions, and some companies, such as J.W. Speaker, even sells heated taillights for trucks and trailers.
Ask a Mechanic is written by Brian Early, a Red Seal-certified automotive technician. You can send your questions to firstname.lastname@example.org. These answers are for informational purposes only. Please consult a certified mechanic before having any work done to your vehicle.
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