Ever wonder how your car defroster works? What are those strange black lines in your rear window? What should you do when your windows fog up? How do all these questions tie together?! Read on, we promise it’ll all make sense in the end.

Why do you need a windshield defogger?

A windshield defogger serves a number of purposes, and it’s one of those parts you tend to forget about until something goes wrong. First, it’s important that we draw a distinction between the front and rear windshield defogger.

The front defogger works by channeling warm air through vents aimed directly at your windshield. The rear defogger works by electrical currents through black fibers running through your rear windshield. Both end up serving the same purpose while operating differently.

How do the windshield defoggers work?

As previously mentioned, rear defrosters work by pushing an electrical current through the fibers, but the front defrosters function by redirecting the air from your air conditioning and heating unit through vents in the top of the dashboard. Using warm air often expedites this process, but it takes time for the heater core to warm up after turning on the engine, causing the air to come out cold in the winter months.

The goal of the defogger is to raise the overall temperature of your windshield to melt ice or cause the condensation from fog to dissipate.

How to know if there are problems with your windshield defogger

• No heat is coming out during the winter. This could mean a bigger issue. You may be low on antifreeze, or there might be issues with your heater core.
• Nothing happens when you press the defogger button. This is likely an electrical issue. It could be a blown fuse or loose wiring.
• The vents might simply be dirty. Clogged with dirt, or covered in debris, the dried air might not have the opportunity to make it through the vents.

What to do if there are issues?

Repairing a broken windshield defogger isn’t usually a simple task and we strongly recommend getting it checked out instead of attempting to repair it yourself. Often there is some disassembly that needs to happen, and there might even be some electrical repair issues. If so, it’s often best to get a professional opinion.