Is there a way to test rear defroster?

On my 2006 Jetta, I suspect the rear window defroster is not working. The button lights up when I press it but it doesn’t clear the window like in my other cars. I know the rear window was replaced with an aftermarket one at some point before I bought the car.

Is there a way to troubleshoot whether it is the switch, the wiring somewhere between the switch and the rear window or the rear window itself?

Bump; fuse number 25, with the 25 amp fuse looks great. I even took that fuse out and put it into another function and it worked, so the fuse is not the issue.

Just a thought here, if the back window was replaced did they ever plug in the defroster in? The defroster is built into the glass, but there has be a wiring connection that connects to it to supply voltage to it. I would check the connection with a volt meter to see if your getting power to that point.

Also check the relay under the dash..... This is where my problem was

Kalter|Tod said:

Also check the relay under the dash..... This is where my problem was

Click to expand...

If I can hear the click when I press the defrost button, would that indicate that the relay is working?

brownnugen said:

If I can hear the click when I press the defrost button, would that indicate that the relay is working?

Click to expand...

Not necessarily. The click sound only indicates that the coil of the relay is energized, which means the magnetic circuit is doing what it is supposed to do (attract the armature). However, the electrical contacts the armature brings together by its movement may be oxidized and thus increase significantly resistance of the circuit the contacts serve.

Found out the word on the driver’s side was not connected. I hooked it up and was able to show voltage on the grid lines. I will “field test” it this week.

brownnugen said:

Found out the word on the driver’s side was not connected. I hooked it up and was able to show voltage on the grid lines. I will “field test” it this week.

Click to expand...

I have this same issue with my '06 Jetta Diesel;
Button lights but apparently no power to the RWD.
I checked fuse# 25 and is in good shape (pulled it out, then back in) still no power.
What is the "word on the driver's side" (wire??) that was not connected (2nd to last post), where is this wire at?
Where do I find the wiring connector to the RWD, at the Rear Glass?
What relay number under the dash does this circuit use?
Are there any other relays/switches/fuses etc. for the RWD?
How can you tell if you have heated rear-view-mirrors, if they don't work-you can't tell?
Thanx ALL, all help is appreciated!!

Do you have VCDS to manually test?


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I am not sure what a VCDS is or how to use it?
How will that help me, where can I get it?
What is approx cost?

VCDS is a piece of software that you run on your laptop with a specific hardware dongle sold by VAG COM. If you own a VW I recommend you do a little googling. Here is a YouTube video where a guy is fixing a rear defroster, you can give this a try as well:

https://youtu.be/n2d-D0RG9Ms


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