View Full Version : Rear defogger issues

03-09-2009, 12:35 AM
Ok so it used to not work at all, was a issue with wiring in the fusebox.

Now, i got it "working" but only the top 3 horizontal lines work. I know there's some sort of "patch kit" that lets you fix the lines if they've cracked/been cut, however, i can't see any cuts in the lines.

Is there a way to isolate the problem?

Is there just one +ive lead on one side, and a ground on the other, or are there a few leads going to the window?


(i'm putting tints on in a few days, and once they're on the opportunity to fix this will be gone, so i'm trying to be proactive!"

03-09-2009, 11:22 PM
ok so i figured it out myself.

The easiest way to determine where the cracks in the lines are is using a voltmeter or a test light. Attach one end to the ground (passenger side connector from c-pillar to copper lines in glass, and wrap tinfoil around the other end (so as not to scratch the copper lines more). Drag the tinfoil across the lines (driver side to passenger) and see where there is no longer 12V. That's the crack, label it, and fix it tomorrow:)

03-09-2009, 11:44 PM
bitchin'...see, don't you love E30s?

the cycle goes like this fix,break,fix,fix,break,fix,fix,break,fix,fix,brea k,fix,fix,break,break,break,break,break,

03-10-2009, 03:42 AM
Let us know how that 'fix it pen' works, if that's what you use. I have seen them a few times and always wondered if they worked or not.

03-10-2009, 03:20 PM
^^i've used them before, had great success, but i'll try to remember to post pics when i do it (likely tomorrow).

03-24-2009, 09:05 AM
what was the problem with your defogger, cause mine doesnt work and the wiring seems fine, any suggestion on what it might be, thanks.

03-24-2009, 12:34 PM
there's two attachments on either side of the "grid" in your rear window, one passenger, one driver.

Driver side is +, passenger side is -.

Get a multimeter, attach the negative side to the connector on the passenger side (its the metal tab that goes from the C pillar to the grid).

Wrap the +ive end of the multimeter in tinfoil (so as to not further damage defogger). Trace the lines (right to left) and see where the voltage drops.

If there's no voltage at all, test it from left connector to right connector. If there's no voltage there, you have a wiring/fuse, relay issue.

03-24-2009, 04:04 PM
Clean the spade connector contacts if all the lines check out.

Mine worked half assed, simply because they aged and lost their conductivity. Short of putting in a new window, there's not much you can do unless you drag that pen across each and every line.

All this is assuming there are no breaks of course.