What Is A Rain And Light Sensor?

What is a rain and light sensor?The rain sensor is a switch activated by rain. It is responsible for automatic windscreen wipers and protecting the internal systems from the rain. It works by bouncing an LED light off the windscreen, which becomes distorted by water on the surface. The light sensors work in a similar way, detecting the amount of light coming through the windscreen. If it is below a threshold then it automatically activates headlights while the car is on.

Almost all modern cars have plenty of sensors. The light and rain sensors are important for monitoring the weather and adapting the car to suit. They are usually found together on the windscreen near the top by the rear view mirror. If there is a problem with them, then the warning light will show up.

The photoelectric ‘light’ sensors activate the headlights during low lights, although they only do this when first switching the car on, as many drivers prefer to manually toggle the headlights while in motion.

There are limitations to both sensors, as different conditions are difficult for a computer to understand. The rain sensors can be thrown off by debris or dirt on the windscreen which alters the amount of light reflected back, the dirt can also affect the light sensors which are blocked off from any light. This can be remedied with a squirt of windscreen wiper fluid and a quick wipe across the windscreen. If the light persists then you may want to have a car wash. The light sensor is also thrown off by fog or intense rainfall since light can still be detected.

What the rain and light sensor warning light means

The light may vary across vehicles, but the image should generally be the same, you can check in your owner’s manual if not. An issue has been detected with either the computer or the system, and will be deactivated. A diagnostic testing code will be saved to your computer for a mechanic to more easily identify the issue.

You can still manually use your headlights and wipers. Reasons for the sensors to fail can be due to a crack/chip repair or a replacement non-factory windscreen.

Is it safe to drive with the rain and light sensor warning light on?

Your headlights and wipers should still be working manually, you just have to remember to switch them on and off. Relying on automatic systems can leave you in trouble when they decide to stop working. You must be prepared to take control of the vehicle in all situations.