rear demisters

Need technical Q/A then you're in the right place

Moderator: martauto

Post Reply
daveyboy20
E30 Zone Newbie
E30 Zone Newbie
Posts: 155
Joined: Wed Oct 10, 2007 11:00 pm
Location: The Wirral

Thu Dec 27, 2007 6:59 pm

The lines don't look damaged at all yet only one line (right a cross the middle) demists. It works very fast but its hard to see out of a one inch strip! Any ideas? Cheers
uzdubmwe30
E30 Zone Newbie
E30 Zone Newbie
Posts: 194
Joined: Mon Jun 19, 2006 11:00 pm
Location: nottingham

Thu Dec 27, 2007 7:02 pm

count yourself lucky, none of mine work! search for the multimeter test on here, it's somewhere around, basically you get a multimeter and check the wires that way.
sam325is
E30 Zone Addict
E30 Zone Addict
Posts: 2002
Joined: Thu Jul 06, 2006 11:00 pm
Location: Cheltenham

Thu Dec 27, 2007 7:07 pm

woa only 1 working is UNLUCKY! on close inspection from the inside of the car you will be able to see the breaks in it. you can then repair them. :D
uzdubmwe30
E30 Zone Newbie
E30 Zone Newbie
Posts: 194
Joined: Mon Jun 19, 2006 11:00 pm
Location: nottingham

Thu Dec 27, 2007 7:11 pm

conductive silver epoxy and masking tape, I can't be arsed to do mine yet
sam325is
E30 Zone Addict
E30 Zone Addict
Posts: 2002
Joined: Thu Jul 06, 2006 11:00 pm
Location: Cheltenham

Thu Dec 27, 2007 7:12 pm

i ahve done a whole rear screen before....and then decided the silver lines looked a bit :gay: so i took it to the scrap yard and got another :cry:
User avatar
Brianmoooore
E30 Zone Team Member
E30 Zone Team Member
Posts: 49358
Joined: Mon Jan 10, 2005 11:00 pm

Thu Dec 27, 2007 7:22 pm

Switch the screen on, clip one lead of a voltmeter to earth, and put the other probe against the tracks, one at a time, in the middle.
The working one will give around 6 volts. The others will give either 0 or 12, depending on where the break is.
Check on the contacts at each side. One should give 0 and the other 12. Then check all the way up and down the vertical traces at the side. The problem I found on two screens I tested a couple of weeks ago was that these vertical traces had corroded away.
Now back to the horizontal tracks: On any track that gave 0 volts in the middle, move the probe towards the 12 volts + side of the screen, until the voltage suddenly jumps to 12 volts as you cross a break.
Similarly, where you found 12 volts in the middle, move the probe to the left until the voltage drops.
Mark the breaks as you go, then repair them with two part epoxy conductive paint and masking tape.
Note that if there are two breaks in any one track, this will only find one of them. Repeat the process to find the second ones, if there are any.
Be careful not to damage the tracks with the meter probe!
It's a fairly simple job to replace the screen with one from a breaker. The one I did a couple of weeks ago took about three quarters of an hour from start to finish, using only a small/medium screwdriver and a pot of silicon grease. Most of that time was spent refitting the locking strip (A job that would take about a minute, if I could find that special tool!!)
goosiegander
Zonegoose
Posts: 2544
Joined: Sun Nov 19, 2006 11:00 pm
Location: East Anglia

Fri Dec 28, 2007 2:11 am

very handy chaps, any hints on where to obtain conductive silver epoxy?

b regards, Goosie :D
uzdubmwe30
E30 Zone Newbie
E30 Zone Newbie
Posts: 194
Joined: Mon Jun 19, 2006 11:00 pm
Location: nottingham

Fri Dec 28, 2007 5:29 pm

maplins bud
smithy318i
Engaged to the E30 Zone
Engaged to the E30 Zone
Posts: 5797
Joined: Thu Apr 28, 2005 11:00 pm
Location: Tyne & Wear

Fri Dec 28, 2007 5:49 pm

your local auto discount shop will sell it.

It comes in a tiny bottle with a brush attachment but dont use the brush as it's too big. I used a cocktail stick when I fixed one of my rear screens.
Image
User avatar
Brianmoooore
E30 Zone Team Member
E30 Zone Team Member
Posts: 49358
Joined: Mon Jan 10, 2005 11:00 pm

Fri Dec 28, 2007 7:33 pm

Use two pieces of masking tape to give a neat repair.
Post Reply