Check Control Display - Backlight stays on ...

[MMunro]

The orange backlight on the Check Control Display LCD on the instrument clluster stays on all the time, whether the car is on or off (1990 525i). What could cause this or what is this a symptom of? All other lights and guages are fine, and the alphanumeric characters display properly, just that rectangular orange glow!!
Any ideas?

[Jared at Pelican Parts]

Dd you check the fuse panel?

[MMunro]

Any particular ones? I just looked at the front fuse box, especially Fuses 1, 17, 20 and 29, which I know have to do with the instrument cluster. They look fine visually.
The backlight is constant, not an intermittent problem, and it seems only the message display part is affected.
I should add that I have been having the classic possible LKM problem, with the low beams cutting out with no message displayed, for over a year now, but that started long before the backlight problem which started in July.
What controls turning on and off the Check Control display? Is it the Check Control Module itself, or is there some other switch?
Thanks.

[Jared at Pelican Parts]

Hmm, I cant remember for certian, but I think these cars have a light control module relay that can sometimes cause problems like this. It should be a long rectangular relay in the engine compartment.

[MMunro]

Yes, there is a Light Control Module / Lamp Control Module in the front fuse box. Usually, the problem you hear people talking about is with the relays for the low beams, intermittent headlights, or messages like TAIL LIGHT, but perhaps there is some connection to the LCD module in the instrument cluster as well. I just thought perhaps someone else might have seen this backlight problem before and solved it.