Question: Rear Window Defogger / Defroster Lines

[bcrdukes]

Hey folks,

I have a 2004 996 coupe. During heavy rain, I noticed the rear defogger / defroster working, however, maybe 3 or 4 lines work properly. Mileage is 53,000km / 33,000 miles. The rear defogger light stays on as it should until about 10 - 12 minutes (I forget exactly.)

What can be the problem? Anybody have this issue?

Thanks!

[bcrdukes]

Follow up #2:

I spoke too soon. Turns out only about 3 or 4 lines work. Any ideas on where else or what to look for?

Edited April 20, 2014 by bcrdukes

[bcrdukes]

Bump.

Any suggestions on where to begin troubleshooting? I can't seem to find any "visible" breaks or scratches on the lines. I'm not sure why or how only 3 or 4 lines work. There's got to be something more.

Perhaps a plug I can trace it back to or relay? Thanks in advance!

Edited May 4, 2014 by bcrdukes

[JFP in PA]

Bump.

Any suggestions on where to begin troubleshooting? I can't seem to find any "visible" breaks or scratches on the lines. I'm not sure why or how only 3 or 4 lines work. There's got to be something more.

Perhaps a plug I can trace it back to or relay? Thanks in advance!

If individual lines on the defroster are out, it is the lines on the glass and not an electrical problem elsewhere.

And please do not "bump", it is against forum rules.............

[bcrdukes]

I'm surprised only 3 or 4 lines work, which makes me question if there is a bigger problem at hand.

In the event the grid lines are presumably okay, is there anything else to check? Is there a plug within the pillar that connects to the rear window?

[JFP in PA]

I'm surprised only 3 or 4 lines work, which makes me question if there is a bigger problem at hand.

In the event the grid lines are presumably okay, is there anything else to check? Is there a plug within the pillar that connects to the rear window?

Again, if any of the lines on the window work, all should work unless somewhere in the window lines there is a break in the ribbon. The window grid is a simply DC heater tape with current flowing through it, it has a single electrical connection on each side. I would suggest you get a magnifying glass and closely examine the lines that are not heating, some where on them is a break in the tape.

[bcrdukes]

I'm surprised only 3 or 4 lines work, which makes me question if there is a bigger problem at hand.

In the event the grid lines are presumably okay, is there anything else to check? Is there a plug within the pillar that connects to the rear window?

Again, if any of the lines on the window work, all should work unless somewhere in the window lines there is a break in the ribbon. The window grid is a simply DC heater tape with current flowing through it, it has a single electrical connection on each side. I would suggest you get a magnifying glass and closely examine the lines that are not heating, some where on them is a break in the tape.

Thanks.

I will take a closer look (no pun intended) and report back. :)

I have also read you can further pin point the break in the line/ribbon using a multimeter, is this correct?

[JFP in PA]

I'm surprised only 3 or 4 lines work, which makes me question if there is a bigger problem at hand.

In the event the grid lines are presumably okay, is there anything else to check? Is there a plug within the pillar that connects to the rear window?

Again, if any of the lines on the window work, all should work unless somewhere in the window lines there is a break in the ribbon. The window grid is a simply DC heater tape with current flowing through it, it has a single electrical connection on each side. I would suggest you get a magnifying glass and closely examine the lines that are not heating, some where on them is a break in the tape.

Thanks.

I will take a closer look (no pun intended) and report back. :)

I have also read you can further pin point the break in the line/ribbon using a multimeter, is this correct?

Correct.