Hello again everybody. Remember that new rear screen I put in 2 years ago? Well, all my efforts at sealing the edges were successful and no delamination, so far....
However, the entire top section has just stopped working - totally cold. Pulled off the interior C-pillar trim to find all the gubbins behind and in parallel checked the wiring diagram. There are actually two equal-sized matrices in the glass, top and bottom, with the two separate blocks of fine wires running in parallel between four edge connectors, an upper and lower on each side..
The edge connectors have a +ve wire on one side and a -ve wire on the other, giving four wires that then go to two oblong-shaped control thingies, one in each pillar. Obviously my problem can be narrowed down to the two top wires, but I'm at a loss to know how to test for voltages and continuity as I suspect some voltage regulation and/or step-down is going on in the "controllers". Has anybody ever got into the nitty gritty on what impedence there should be across the matrix? Or what range of voltages should be present on the supply wires?
I'd be grateful for any small tidbit of information that helps me to isolate the window (Lifetime Autoglass warranty here I come!) or indeed the car wiring at the faulty bit.
Cheers
Rear screen heater problem
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Very straightforward. 12V at the supply side and the other should be earthed.
8Tech.
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The other "thingies" are probably the antenna amplifiers. The antenna for the radio is with the matrix of heating wires in the screen (although electrically separate, I think).
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Zitat von sprucegoose;66023
Thanks. As you said, I did indeed find 14.2V (engine on) across each set of supply wires once I'd worked out which wire was which. So I thought, why not make it easy and just switch the top and bottom supplies? Problem identified in one: bottom still gets hot but top doesn't.
To be double sure, then checked the impedence across the window: 2.3 ohms at the bottom - open circuit at the top. Sadly, this means the window is knackered and its less than 2 years old. Will post how I get on with Autoglass. Should be interesting....There must be a break somewhere that cuts the line totally.
If you're able to find this there are ways to repair this and not remove the window...special kind of paint can be applied. -
Zitat von Algernon;66027
There must be a break somewhere that cuts the line totally.
If you're able to find this there are ways to repair this and not remove the window...special kind of paint can be applied.I agree on an old screen but if I had paid for a new screen I would require it is replaced under warranty.
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The repair of these screens is difficult, if not impossible, because the ultra-fine wires are embedded between two layers of laminated glass. This is different to the more usual and wider, red-brown copper depostitions found on the back of more conventional screens. A conductor break in these can be reapired with conductive paint.
The e31 rear screens tend to delaiminate at the edges, if the rubber seal around them starts to let in moisture. This then creeps in between the two layers of glass and starts to corrode the conductors. Usually the faults appear on the thick strips along the left or right edges of the screen. If it is here, it might be possible to drill or dremmel the glass at the side sufficiently to get some of this condcutive paint inside to bridge the break. However, this is not easy.
(The only other manufacturer that I know of that used similar rear screens was Mercedes with the contemporary R129 SL.)
If your screen was brand new to begin with, then it may be some other kind of fault that has caused the break, or the ruber seal was not fitted with sealing mastic.
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Spruce when I first got my car it did not demist so I resoldered the connection on the side of the screen and that fixed mine as it must have been a dry joint. I used a gas powered soldering iron with a fine flame tip as it helped me to direct the heat fast.
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I would have to say that the moral of this story is DO NOT USE AUTOGLASS,
their product is clearly (pun) inferior and I would persue this further. Not sure how much you paid but BMW would not hesitate to replace it under warranty.My Independant auto glaziers would also change that under warranty.
8Tech.
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Didn't actually think about this...
If the wires are actually embedded there is no realistic way to correct a broken wire (or resistor wire).
Made the mistake based on my Ford that has one wire corrected with this method.
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Well done -
Well done mate, 10/10 for endevour I'd say.
good work ,don't let the bar stools grind you down, glad it worked out
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Top tint?
I see no top-tint on your rear screen?
OEM was top tint.
I had same issue....none in country I was told.
Any others with similar experience?
Have BMW stopped making this? -
Poor quality glass fitters..........
Had 3 rear screens replaced in 2 yrs by BMW under warranty because of electrical issues in the wiring.
All very well and good, but 3 years later I then had corrosion appearing because of poor quality workmanship when fitting those screens.
Think in hindsight I'd be inclined to live with a few elements 'out' and not tempt fate with the future demon rust............... -
Zitat von David8;67083Alles anzeigen
I see no top-tint on your rear screen?
OEM was top tint.
I had same issue....none in country I was told.
Any others with similar experience?
Have BMW stopped making this?On my cars it build sheet it specified top tint as a optional extra
are you sure on this?
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