The black box on the windshield behind the mirror. What is its role?

The black box on your windshield seems mysterious and ominous, doesn’t it? You’ve probably wondered to yourself whether there really is a black box in your car—and what that box does, anyway.

Don’t worry—you’re not the only one who feels this way!

In this article, we’ll cover everything you need to know about the black box on your windshield, so keep reading to learn more about it!

What is the Black Box on Windshield Behind the Mirror?

This black box is the remote control door lock receiver which has the antenna for taking signals from the tire pressure sensors and your remote key fob. This box also has the Air Moisture and Windshield Temperature Sensor used for the HVAC auto defog function.

Can the Black Box Fail?

Yes, the black box can fail. If the antenna or other components in the box fail, then your car will not be able to receive signals from the remote key fob or tire pressure sensors.

This can cause your car’s doors to not lock or unlock properly, and the HVAC system may not be able to defog the windshield correctly. In some cases, the black box may need to be replaced if it cannot be repaired.

Causes of Black Box Failure

One of the most common causes of black box failure is water damage. If your car gets caught in a flood or you drive through a deep puddle, the water can damage the circuitry inside the black box.

This can cause the system to fail completely or just start acting erratically.

Other causes of black box failure include:

  • Physical damage – if the black box gets hit by a rock or other object, it can fail.
  • Electromagnetic interference – can come from things like power lines, cell phone towers, or even garage door openers.
  • Corrosion – if the black box is exposed to salt water or other corrosive materials, it can corrode and fail.

In addition to failing, a black box can also suffer from poor signal quality. This can happen if something interferes with its radio frequencies or prevents it from receiving signals at all.

If your key fob or tire pressure sensors aren’t working, then your black box might be suffering from poor signal quality.

The best way to fix poor signal quality is to first verify that nothing is blocking any of the antennas and then try moving them closer together or further apart until you find their optimal distance.

How to Fix the Non-Functional Black Box?

If your black box is not working, there are a few things you can try to fix it. First, check the fuse. If the fuse is blown, replace it with a new one. Next, check the wiring. If the wires are loose or damaged, they will need to be repaired or replaced.

Actually, seeking out repair work from experienced professionals who specialize in automotive electronics could save you time and money in the long run.

You may want to get an inspection for a full diagnosis before repairing anything yourself. When you do seek out repair services, make sure that the technicians have experience with specific brands and models of cars so that they can diagnose any problems quickly.

Disposing of Old Black Box

After you have disconnected the battery, you need to remove the black box from your car. Make sure to disconnect all wiring harnesses and electrical connections before lifting the black box out of your car.

Place it in an appropriate container and take it to an authorized recycling facility.


So, the next time you see a black box on a windshield and wonder what it is, now you know! It’s the remote control door lock receiver, which has an antenna for taking signals from the tire pressure sensors and your remote key fob.

This box also has the Air Moisture and Windshield Temperature Sensor used for the HVAC auto defog function. While it may seem like a mystery at first, it’s actually a pretty simple explanation.

Remember that this type of car equipment can be cumbersome to install if you’re not a professional.

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