How To Fix A Heated Rear Window

How To Fix A Heated Rear Window?

Perhaps, a rear window heater is one of the most crucial elements in a car. It helps improves visibility and road safety, especially for people living in the colder parts of the world. However, what would happen if your car’s heated rear window stopped working? How would you fix it?

Whether it’s a blown fuse or faulty wiring, or basically any problem in the circuit, to help you navigate through such issues, we have curated a guide on how to fix a heated rear window that even a dummy can understand. Want to know how to fix a heated rear window using conductive paint? Or how to fix a blown fuse using an ohmmeter? Keep reading because, in this article, we will discuss all the possible solutions in detail.

How does a heated rear window work?

A defogger or a heated rear window is, simply put, an element that helps the rear window of a car to heat up via electrical current. The electric current induces resistance, generates heat, helps melt ice, and reduces fogginess.

Signs your car’s heated rear window isn’t working properly.

Your car’s heated rear window can stop functioning properly for many reasons, such as a faulty wire, damaged switch, poor earth connection, damaged switch, etc. However, before learning how to fix a heated rear electric window and deducing the reasons that stop it from working properly, you should be wary of the signs that point towards a faulty defogger.

Following are a few of the signs that your car’s heated rear window is not functioning properly:

  • Doesn’t clear windows instantly:

One of the most evident signs of a functioning defogger is that it starts clearing the windows as soon as it is turned on. If the opposite happens, then it’s a clear red flag.

  • Doesn’t light up:

 If your defogger’s button doesn’t light up, it hasn’t turned on.

  • Works inconsistently: 

A clear sign that a defroster’s switch needs attention is when you notice your heated rear window working sometimes and not functioning properly other times. Get it fixed before it shuts down completely.

How to fix a heated rear window?

Your car’s heated rear window can stop working for many reasons, most of which have been mentioned below. Let’s gauge a deeper understanding of these reasons and also discuss the solutions to these problems:

1.            Blown fuse

A blown fuse is the most recurring and common problems for a heated rear window. Your ohmmeter should show a reading of 0 ohms to indicate that your fuse is working just fine. If not, then you need to replace the fuse.

If your fuse has blown, you will have to replace it and check your defroster again to see if it is working. However, if the fuse blows when you turn your defroster on, then it indicates that there has been a short circuit.

  • Modern heaters:
    If your car’s heater has been installed by your car’s manufacturer, your heater’s fuse is connected with other circuits, and you’ll find the fuse in the fuse box.
  • Older heaters:
    Inside the glass, the older defroster versions are made. Thus, if these heaters become dysfunctional or stop working, you will have to install a new screen.

At least one of the two fuses should have a voltage of 12 volts. However, if the defroster is still not functional, you need to check the power despite the voltage being induced and maybe consider fitting a new voltage regulator.

2.            Conductive paint

Often, there is a break in the heater’s element, which prevents it from functioning seamlessly. To find where the break occurs, you need to inspect every defroster element. Once you have figured out where the break is, you need to:

  • Clean the surrounding glass carefully without damaging it.
  • Cover every broken element properly with a masking tape
  • Then, cover the break with a thick coat of conducting paint and let the paint dry for 20 minutes.
  • After the paint has dried off completely, apply a second layer of conducting tape and take the masking tape off.

3.            Checking the test lamp

Connect your defroster’s lamp to an earth point and then poke the fuse’s input side. If the lamp doesn’t light up, then check for breaks in the wiring connecting the fuse and breaks; however, if it does, then check if the input terminal is conducting current.

Check the relay

If you have had your defroster installed by a car manufacturer, your rear window heater would consist of a relay- a small box close to the fuse box. Turn the heater’s switch on and off and check the relay box for vibrations. If there are no vibrations, you will have to get the relay replaced.

Check the lamp’s switch for faults. If the switch isn’t faulty, check the switch for burn signs and if it is effectively operational. However, if the switch is not working, it will have to be replaced.

4.            Check the heater element

If you cannot find any fault in other aspects of your defroster, there are high chances that your heater element is problematic. Check every strip of your heater element for breaks and faults and then repair or replace the strip depending on your heater type.

5.            Check the earth wire

Lastly, if your heater element is also functional and free of breaks, but your defroster is not operational, and you’re still wondering how to fix a heated rear window, then look for breaks and your battery connections in the heater’s element earth wire. Make sure that the earth connection is free of corrosions and is clean. If it isn’t, clean it with paper and apply Vaseline on it to stop it from rusting further. Some people also use rust convertors to ensure to prevent corrosion.


For every driver, gaining knowledge of the basic ins and outs of how their car functions is an essential skill set. We are often left to deal with our problems on our own, in times of emergency because life is uncertain. This is why learning how to fix a heated rear window will save you from great hassle in times of need and help you save tons of money that you would’ve otherwise spent on consulting a mechanic.