Can you add a rear window defroster?

Overview

Adding a rear window defroster to a car that didn’t come with one from the factory is possible but can be tricky. There are a few things to consider before deciding to take on this project.

What does a rear defroster do?

A rear window defroster uses a grid of thin wires affixed to the inside of the rear window. When turned on, an electrical current passes through the wires, heating them up to quickly clear frost, fog, and snow from the surface of the glass. This helps restore visibility out the back of the vehicle.

Rear defrosters improve safety by giving the driver better rearward visibility in cold weather. They are considered a standard feature on most new vehicles today.

Is it possible to add aftermarket?

It is possible to add an aftermarket rear defroster to a vehicle, but it requires some wiring work. The main steps include:

• Installing a defroster grid kit on the inside of the rear glass. This comes with the thin wires and adhesive backing.
• Running wiring from the battery to a switch on the dashboard.
• Installing a fuse for safety.
• Connecting the wiring to the defroster grid.

Aftermarket grids are available for most vehicles, though some newer curved rear windows can be challenging to retrofit. Carefully following installation instructions is crucial to get proper functioning and avoid electrical shorts.

Professional installation is recommended if you’re not experienced with automotive electrical work.

Considerations before installing

Here are some important factors to think through before taking on a rear defroster addition:

Cost

Parts and labor can make this project expensive, easily running $200-500+ for parts alone. Factor in wiring, the switch, fuse, connector, and professional installation labor if not doing it yourself.

Complexity

This job requires wiring knowledge, splicing into existing wires, interior panel removal, and neat routing of new wires. If you don’t have experience, have a professional handle it. Mistakes can lead to electrical gremlins or serious hazards if improperly wired.

Rear window condition

The defroster grid kit has to adhere cleanly to the glass. Pitted, foggy glass or prior tinting with adhesive residue will prevent proper adhesion. The rear window may need replacement to provide a clean surface for grid installation.

Vehicle compatibility

Some vehicles are easier to add defrosters to than others. BMWs and Mercedes for example integrate defrosters into their complex safety electronics. This can make aftermarket installation extremely difficult without dealer reprogramming. Check your specific vehicle’s feasibility.

Features and technology

Factor in other features that may be useful to add at the same time for wiring ease. This includes a rear wiper, rear camera, or antenna for radio signal amplification. Pre-running wires for future gadgets can also be smart if opening up interior panels.

Depreciation

Assess the value add of a defroster versus simply buying a vehicle that already has one. Some older or cheaper vehicles may not justify the expense of adding this feature. Also factor in potential impacts on resale value.

Installation steps

If moving forward with adding a rear defroster, follow these general steps:

1. Buy defroster kit and confirm it’s compatible with your vehicle’s rear window shape.
2. Clean inside of rear glass thoroughly and check for any damage or tint.
3. Remove interior trim panels to access wire routing paths.
4. Run wiring from battery positive/negative terminals to switch location.
5. Install switch in accessible dash location.
6. Connect wiring to defroster grid terminals.
7. Thoroughly test operation and check for any electrical issues.
8. Reinstall all interior trim panels.

Be prepared for this to take a full weekend or longer for novice mechanics. Have your vehicle’s wiring diagram handy for reference.

Conclusion

Adding an aftermarket rear defroster is convenient but requires careful planning. Assess costs, complexity, vehicle compatibility, value, and your own DIY skills before deciding. Proper installation is also critical for safe, reliable operation. In many cases, investing in a vehicle that already has this feature can be the smarter and easier choice.