Your car’s cabin protects you and your passengers from the elements, harsh sunlight, wind and more. However, having an enclosed cabin can lead to visibility problems when the air is particularly humid. While your front defogger works through the air conditioner, that’s not the case for the back glass.

Most vehicles manufactured today come with a rear defogger switch. Pressing this switch activates an electronic defrost system that is either overlaid on the rear window or actually embedded in the glass itself. Take a look at your back window and you should see wires running across it. That is your defroster. It’s connected inside the car to the vehicle’s wiring harness.

While problems can develop in the wiring system itself, the most likely point for trouble to start with the rear defogger is the switch. It’s electronic, and thus subject to failure. There is no set time limit for how long the switch will last – it’s more about use, as well as oxidation. The more frequently you press the defogger button, the faster it will wear out. It’s like your window switch or door lock switch. The contacts wear out through use.

Another potential issue with a rear defogger switch is potential oxidation of the internal pins. This is normally only seen in vehicles driven in areas where the humidity is very high most of the year.

While not having a working rear defroster won’t keep you off the road, it does create visibility problems, which means it is a safety issue. Here are some of the symptoms to watch for that might indicate your switch is about to fail:

  • Switch only works intermittently
  • Switch will not turn on
  • Switch will not turn off
  • Switch sticks in place

If you’re experiencing any of these symptoms, then a certified mechanic can help by inspecting the rear defogger switch and replacing it if necessary.

This article originally appeared on YourMechanic.com as How Long Does a Rear Window Defogger Switch Last? and was authored by Valerie Johnston.


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