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Coyote_ar
04-12-2017, 01:57 PM
Hi guys, so my car had, as most e34s do, the problem with the capacitors.
My speedo would go out, my fuel tank indicator would indicate random levels, and the backlights of the LCD displays wouldnt work intermitently (the LCD did work just fine, you can see them with reflection from the sun or any other light source).

I changed the 5 damned caps, and now everything is working ... except for the freakin LCD backlights. They still go out every now and then. Im not 100% sure, but i would swear its more prone to doing it on cold and humid days/nights. During summer it seemed to be working mostly all the time. Now that summer is over, and its starting to get cold at nights, its getting worse.

I changed the instrument cluster dimmer, since the original one was not working correctly along the whole path.
All the light bulbs on the cluster are new.
I get perfect ilumination for all the cluster, dimmer works just fine, all dials work as they are supposed to. But some days, the backlights of all the LCD displays, just go off. And maybe after driving for a while, they just go on again.

When swapping the caps, i checked to be sure there was no damage to the PCB, no rust. I cleaned the contacts where the light bulbs plug.

Im out of ideas, any clue how to fix this?
Its annoying since i cant see in what position is my trans selector. I need to go to P and start going down again.

Thanks for your help.

shogun
04-12-2017, 05:10 PM
The LCD bachlight is controlled by a light sensor in the middle of the cluster between speedmeter and RPM meter. Easiest would be you get another cluster and swop the LCD display.
Or google for LCD Display Pixel Repair Ribbon, BMW E34
http://www.ebay.com/itm/Speedometer-Display-LCD-Pixel-Repair-Ribbon-Cable-For-BMW-E34-5-Series-1988-1996-/371686126190
http://www.pixelfix.net/eng/bmw.html

Coyote_ar
04-12-2017, 06:33 PM
is that ribbon cable present on all versions of the cluster? Mine is the earlier one, the greyback.
what is the function of that light sensor? is it meant to dimm the lights on the cluster based on the ambient light or something like that?
i dont think the early clusters have it. Its the little circle on top of the ASC light?

as for getting another cluster ... thats not an easy option for me. i would rather try to fix it.

shogun
04-13-2017, 01:12 AM
Should be all the same on E34 and E32 with check control.
The light sensor/photocell regulates only the check control lights, such as the warnings, the gear and mode indication.
The rest of the cluster is regulated with the dimmer switch
http://www.e38.org/e32/BMW_pdfs/INST_info.pdf

Coyote_ar
04-14-2017, 01:24 AM
Ok, i thought it was the circle. Its actually the rectangle below them. Yes i do have it.