Volume 12, Issue 3 - May/June 2010


Working with Rain and Light Sensors
Handy Tips for Dealing with These During a Replacement
by Joseph Gold

Installing rain and light sensors correctly is critical in order for them to work properly. Air bubbles or contaminants, such as dust between the adhesive and the glass, can cause them to malfunction and must be avoided. Windshield manufacturers utilize special heating devices and vacuum systems for their application processes. It can be difficult for a technician in the field to apply sensors without these tools, but here are some tips and guidelines.

Pre-Inspection and Functionality Test
Before getting started on a windshield with rain sensors, you first need to make sure that the rain and light sensors are working. Here are a few tips for doing so:
• Prior to the removal of all windshields with sensors, functionality needs to be proofed by spraying water onto the glass; and
• For combined rain and light sensors, the light sensor functionality needs to be proofed by darkening the light sensor section on the outside of the windshield.

A sensor that does not operate correctly on the original glass will not work on the newly installed windshield either. Sensors not operating correctly need to be calibrated by the local OEM dealership before the broken windshield is replaced.

“A windshield with a rain and/or light sensor is developed to
operate within that specific windshield’s parameters.”

Once you’ve completed the above pre-inspection tips and have replaced the glass, it’s time to re-install the rain sensor. There are several important steps involved in this.
• First, use a 50/50 mix of isopropyl alcohol and water to clean glass surface. Most companies supply a small capsule of primer with a new sensor. Apply the primer to the glass just before applying sensor.
• Try to always get new sensors with the adhesive pad pre-applied. If you have to apply your own pad to a sensor, there is a chance that it may incorporate air bubbles and/or contamination that may cause it to malfunction.
• It is best to apply the sensor to the windshield if the surface of the adhesive is heated (after the lining is removed). It should be noted that the pad carries a slight electrostatic charge, which will attract dust. Because of this, using hot air from a heating gun is not recommended. The best method is to use radiant heat, like the heat generated by a lamp.
• Once the surface of the adhesive is heated, apply the sensor using a rolling motion while applying pressure. The goal is to push out all air bubbles.

Sensor Hints and Tips
Once you have re-applied the sensors, you will, of course, want to test them to make sure they work.

In order to assure correct testing of the sensor functionality, make sure that all vehicle’s doors are closed and the motor is running, because in many cases (such as in that of the Mercedes-Benz), sensors will only operate when all doors are closed. The vehicles were made this way to make sure that vehicle occupants are not splashed with water by the windshield wipers when entering the vehicle.

Also, be sure not to turn the ignition on or listen to the vehicle’s radio while a vehicle with a rain sensor is without its windshield. This can cause the electronic device to come out of adjustment and it will need to be recalibrated. This happens is because when the radio or ignition are turned on without the windshield in place, the sensor unit receives the wrong information.

Other Factors
There are many other factors to consider when working with windshields with rain and light sensors, such as glass thickness, tints, coatings and a variety of PVB interlayers on the market today.

A windshield with a rain and/or light sensor is developed to operate within that specific windshield’s parameters. The electronic device attached to the optical unit processes the incoming data and reports the information to the electronic controller, which activates the wipers and/or headlights in turn.

If you replace the originally installed windshield with a new one (with a different tint, coating, interlayer or thickness), the electronic device may need to be changed as well. For example, a Mercedes Benz C-Class windshield in solar extra-blue tint (FW02473) has a different electronic device attached than the green/grey tinted (FW02271) glass for the same C-Class vehicle.

Other Types of Sensors
It should be noted that all of these instructions apply to the most common types of sensors found in the field. These all utilize a foam acrylic adhesive. There are other sensors that utilize different adhesives and involve other application guidelines.
These include:
Lexus and Toyota sensors: Have their own unique adhesive. Do not try to use any aftermarket alternative if it is not the same as the OE adhesive. It will not work properly.
Condensation sensors: Need to be applied to the glass specifically in relation to the rain/light sensor.
Today’s new generation of sensors: Use a “gel” instead of an adhesive pad. It is important that this gel is used for the sensor to work properly.

Joseph Gold is the president of Gold Glass Group in Bohemia, N.Y. Mr. Gold’s opinions are solely his own and not necessarily those of this magazine.

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