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Things You Should Know About Your Car’s Rear Window Heating

Car Rear Window Grid

Winters in Australia may be mild, but some regions still experience snow, frost and foggy roads. Maintaining excellent vision is paramount and luckily, car manufacturers have thought ahead. When temperatures drop to zero or below, window defrosters, clear condensation and thaw frost from your car’s windshields.

Your rear window heater allows you to drive with perfect view out of the back of your car. A non-functioning heater can cause serious trouble. Your car’s rear window might not be fogged or iced up all the time, but you don’t want to stop the vehicle and get outside to clear it every time it does.

This article answers the most common questions car owners have about rear window heaters, including:

  • What does a rear window defroster do?
  • What are the effects of heat on a windscreen?
  • Does heat from the grid affect my windscreen wipers?
  • What is wrong with my car’s rear window heating system?
  • Can rear window heaters be repaired or replaced?
  • How do I repair the defrosting grid myself?
  • When should I get my rear defroster repaired professionally?
  • What are the costs for rear window heating repairs?


Car Window Frost

What Does A Rear Window Defroster Do?

Rear window defrosters are used in the backglass of your car and improve clarity and vision out of the back windscreen. They’re an important safety feature, especially if your car is parked outdoors during the winter months.

You might already have noticed a series of parallel grid lines in your backglass and wondered what their purpose was. Those lines are the rear windshield’s heat conductors: The defroster uses an electrical current sent through a grid made of metal and resin. The grid is attached to the surface of the glass using an adhesive. The applied heat dissolves ice and fog, allowing you to drive safely and with clear vision.

Defrosters are very useful: Sometimes you don’t have the time to scrub ice off your car windows on your way to work or to drop the kids off at school. Sometimes the windows fog up while you’re driving. With window defrosters in place, that’s no longer a problem.

Automated Rear Window Defrosters

Automated defoggers turn off by themselves after a time period of approximately 15 minutes. Normally, most defogging or defrosting is completed within that time frame. At said point, the inside of your car has usually warmed up enough to prevent any further fogging. If your car’s rear window defroster doesn’t switch off automatically, a telltale on your vehicle’s dashboard should remind you to turn it off.

Car Windshield Defroster

Clear Windscreens for More Safety

A clean and good-looking vehicle is the pride of many car owners. However, cleanliness and good visibility also play important roles in road safety and should therefore be high up on your priority list.

Your car’s windscreen visibility is a major aspect for the overall safety of your vehicle. You’re putting yourself, your car passengers and people on the road in danger if you don’t pay attention to these details. So don’t slack and make sure that your windscreens are always in the best possible condition.

Dirt, ice and fog aren’t the only factors that may restrict your vision on the road: You should also watch out for small cracks in your windshields. They can reduce the effectiveness of windshield wipers and window defrosters and turn into a bigger issue as time passes. As soon as you notice them, you should get small dents, chips and cracks repaired by your windscreen repair specialist.

Rear Window Defroster – Frequently Asked Questions

What are the effects of heat on a windscreen?

If your windscreens are in excellent condition, changing temperatures shouldn’t affect them. They are built to withstand severe summer heat and temperatures below the freezing point. But a change in temperature can expand and contract the glass, putting it under increased stress. Whilst both glass and defrosters are designed to not meddle with the overall quality of your windscreen, a tiny chip in your rear window can quickly expand itself into a whopping crack when exposed to high temperatures.

If you crank up the heat in a car that has been parked outside over the night, the clash of hot and cold temperatures puts the car glass under immense pressure. Your windscreens can be weakened to a point where small chips become a problem.

Once a crack becomes too big or crosses certains points of the screen, it might not be possible to save the windshield. Then, you have no other option but to get a replacement screen. If you find any damage to your windshields, we recommend seeking expert advice as soon as possible!

Froston Car Window

Does heat from the grid affect my windscreen wipers?

Yes, the heat emitted from the grid of your rear window defroster affects your windscreen wipers, too. Most manufacturers will add extra heating elements close to the position where wipers are resting on the shield. The warmth frees wipers from ice and snow, allowing them to do their job properly and move without restriction.

What is wrong with my car’s rear window heating system?

If your rear-window defroster grid refuses to clear up your windscreen, driving blind is clearly a bad idea. Instead, you should identify the source of the problem and avoid further damage to the defroster grid.

There are a number of possible causes for broken rear window heaters, including a blown fuse, a broken wire, a damaged heater element or a bad earth connection.

One of the most common rear window heating problems is a blown fuse. The fuse is supposed to protect the heated rear window circuit. A simple fuse check will tell you if it has blown and needs replacing. If you swap out the old fuse and the grid still won’t function as intended, there may be a short circuit in the switch or wiring.

If the electric current reaches the heater element, check the element earth wire. There shouldn’t be any broken cables and the earth connection should be clean and tight. Any corrosion, a disconnected wire or dirt can cause an interruption in the circuit.

If nothing appears to be wrong with the voltage, the problem might be the grid itself. It’s easy for the terminals at the grid or the grid itself to become damaged.

Can rear window heaters be repaired or replaced?

A faulty rear window heating system can be a headache! Your first instinct may be to scrape the ice off yourself, but that isn’t very practical in the long run. Plus, you’re risking to make things worse. Since modern grids are basically thin layers of paint printed on to the glass’ surface or stuck on with special adhesive, using force will not solve the issue.

Luckily, small breaks in these heating elements can easily be repaired using a conducting paint. You can choose to do this at home, using a DIY repair kit, or consult with a specialist who can repair your broken rear window heater in no time.

Please note: Older car models may still have heaters with elements inserted into the windshield itself. Unfortunately, it isn’t possible to repair such a heating system. If that’s the case for your car, you might need to have a new window fitted.

windscreen rear window novus

How do I repair the defrosting grid myself?

Fixing a broken rear windshield heater is oftentimes something you can do yourself. If your defroster isn’t working properly, there are a few things you can do at home before calling an expert:

The most common issue is a simple connection break. Make sure that the tabs carrying electricity on the side of the window are attached. Over time they can loosen and interrupt the circuit. You can do this using a tab adhesive product.

If the connection is not the issue, the problem might be the grid itself. The decline of your rear windshield defroster is usually gradual. You might find some parts of the windscreen clearing whilst others stay covered in frost or fog. This is an indicator for breaks in the defroster grid, which are easy to prepare by painting on conductive paint.

If you like doing smaller car repairs, you’ll find this a fun little project. All you need is a defroster or defogger repair kit and 30-minutes of your time. And don’t worry: Defroster repair kits come with all the tools required for the job. They even contain a small stencil that’ll help you connect existing grid lines where they are broken.

But, if you prefer to save yourself the hassle, you should consult an expert to repair your broken windscreen heater. In terms of safety and accuracy, it’ll always be the best solution.

When should I get my rear defroster repaired professionally?

If your defroster isn’t doing its job and you feel unequipped to look into the issue or are simply running short on time, it’s wise to pass the issue on to an experienced windshield repair technician. Remember: You may be able to drive the car without a functioning defroster, but you’d be putting yourself and others in danger. Therefore, we recommend you get your defroster fixed as soon as possible – especially during the colder months of the year.

What are the costs for rear window heating repairs?

Rear window heater repairs can vary in cost, depending on the source of the problem. Different cars have different types of defrosters. Your windshield repair technician will have to take a look at the damage first before they can give you an exact estimate on pricing and duration.

Most rear window heaters can be saved, so don’t put off repairing a non-functioning defroster.

Contact the windscreen repair and replacement experts from NOVUS Auto Glass to make an enquiry or to get a quote. NOVUS’ expert auto glass technicians understand best practice in windscreen restoration and use only the highest quality products.

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