BMW E32 750iL dashboard message display backlight still on after ignition key off

**ivo1st** · 10-14-2013, 09:12 AM

Hello there,

I am happy to find this place

I am new to the forum and I find interesting stuff here about BMW. You are doing a great work here I am happy to join this community. I am recently working on a BMW E32 750 IL '88 and I am trying to get most of the goodies in this car working.
I am getting a strange problem with my dashboard message display. It just happened couple of days ago, before that everything was OK. When I turn the ignition off, after 10-15 seconds the message display backlight goes on, and stays on. Sometimes it happens to start blinking and the car speaker beeps in sequence with blinking. Also the fuel, fuel consumption and temperature gauges start moving. I had changed all of the capacitors in the dashboard one year ago, because it was having behaviour on its own. So I thought that I had stumbled across bad capacitors again and I changed them yesterday, but this problem still occurs. I noticed that when I unplug the X507 connector it stops doing that weird stuff. I looked at the schematics of the dashboard, but I did not understand the relation between X507 connector and what's going on. I have not given up, and I am still looking on the schematics.

I will be happy if someone can throw a light on the problem!

**shogun** · 10-14-2013, 10:15 AM

X507? Or do you mean X502, one of the plugs in the back of the cluster.
But your 1988 E32 does not have X507, it apparently does not exist on your car?
http://shark.armchair.mb.ca/~dave/BMW/e32/e32_88.pdf

The E32 cluster has the following plugs: X16, X17, X271, X502
http://www.e32-schrauber.de/bmw/date...0-2-ws-mod.jpg
For your 1988 with the grey backplate cluster the X16 is this
http://www.e32-schrauber.de/bmw/date...ung-x16-88.pdf
and the rest is all the same for grey, white and blue back cluster
X17 http://www.e32-schrauber.de/bmw/date...legung-x17.pdf
X271 http://www.e32-schrauber.de/bmw/date...egung-x271.pdf
X502 is the white plug http://www.e32-schrauber.de/bmw/date...egung-x502.pdf
and there we have again the transmission
pin 4,5,6,11 gear indication
pin 8,9 transmission program

E= Eingang = in
A = Ausgang = out
Kabel = cable
Ziel = goes to...
Beschreibung = description
gehoert zu = belongs to...

Your car is EURO spec.
EGS= with S-E-M switch
AGS was only available from Modell 93 = from 09/1992, switch is "S-E-M" for EGS, for AGS only "A" and "+", and the TCU control modul has 55 pins for AGS and the EGS 35.

**ivo1st** · 10-14-2013, 10:34 AM

I am sorry for this misleading X507, it is X502 indeed.

**shogun** · 10-14-2013, 11:12 AM

check X502/14 (white 26pole plug, respect. that counterpart on the cluster). That is the ilumination line/wire. When you switch on the parking light, on this line should be ~12-13V.
When light is switched off, there should be zero V.
If not, it might be a problem with your light switch.
pin 14 E=in 0,5 grau/rt = grey/red Beleuchtung/ilumination Kombiinstrument = cluster

**ivo1st** · 10-14-2013, 02:09 PM

A little update on the problem. Today I disconnected the X502 connector and left the others plugged. While I was doing some other stuff I saw that the message display backlight went on again when the ignition is off. I disconnected X271 and no change. It goes off when I disconnect X16 or X17. I am starting to think that the problem is in the dashboard.

Addition - the whole cluster is not illuminated, only the message display backlight remains on without any text on the display.

**Derek K** · 10-14-2013, 09:56 PM

Welcome to the best car forum on the net, (no matter what the vehicle).

**ivo1st** · 10-20-2013, 07:25 AM

I took a picture of what I see on the message display:

**shogun** · 10-20-2013, 10:18 AM

The check control area = the picture you posted is not controlled by the light dimmer but by a photocell between speedmeter and RPM meter.
http://www.e38.org/e32/BMW_pdfs/INST_info.pdf

**Golfball** · 11-01-2013, 10:36 PM

Excellent forum, indeed!

I just purchased a 1989 E32 for my son. Our car has exactly the same issue with the check control backlight as ivo1st described. The door chime on ours also turns on steady after an hour or more after the car has been parked. The two problems appear unrelated, but both can be reset simply by turning the ignition key to the first position.

i'm thinking of removing the cluster and replacing the capacitors if I can ever get the car away from my son. If either of you find the cause, please let me know. If I figure it out, I'll reply as well.

Thanks for spending so much time helping us noobs, shogun.

**shogun** · 11-03-2013, 06:50 AM

Here some excellent repair infos for the clusters from pet in Germany
http://www.pet-racing.de/E34/UNTERLAGEN/KI/KI_REP.htm

**Golfball** · 12-29-2013, 09:57 PM

Time for an update:

A couple of weeks ago, I replaced the Check Control Module with a used part I purchased online. It did not clear up the backlight problem described earlier, nor did it clear up my parasitic current draw (approx. 200 mA) on fuse 20. I suppose the replacement CCM could also be faulty, but it was cheap and worth a try.

So, I finally pulled the instrument cluster (early '89 with the grey back) and replaced the five dash capacitors on the upper part of the circuit board. One of the capacitors had ruptured and was obviously bad. Unfortunately, the replacement capacitors did not resolve the message backlight or current draw issues, either. They seem to have resolved the intermittent fuel and temperature gauge problems, though, so I'll consider it a small victory.

I'm still hunting for the cause of the message backlight and the current drain on fuse 20 problems. I'm hoping they're related. I'll post back if I find anything.

**shogun** · 12-29-2013, 11:04 PM

http://shark.armchair.mb.ca/~dave/BMW/e32/e32_89.pdf
fuse 20
anti theft system, DWA
IHKA automatic climate control
brake lining warning
central locking
EML electronic throttle control (in case it is installed)
instrument cluster / check control
on board computer OBC
park ventilation
park/tail/underhood lights
power windows ZKE
sunroof ZKE

**EEDegreeToDrive** · 01-05-2014, 11:13 AM

Originally Posted by Golfball

Time for an update:

A couple of weeks ago, I replaced the Check Control Module with a used part I purchased online. It did not clear up the backlight problem described earlier, nor did it clear up my parasitic current draw (approx. 200 mA) on fuse 20. I suppose the replacement CCM could also be faulty, but it was cheap and worth a try.

So, I finally pulled the instrument cluster (early '89 with the grey back) and replaced the five dash capacitors on the upper part of the circuit board. One of the capacitors had ruptured and was obviously bad. Unfortunately, the replacement capacitors did not resolve the message backlight or current draw issues, either. They seem to have resolved the intermittent fuel and temperature gauge problems, though, so I'll consider it a small victory.

I'm still hunting for the cause of the message backlight and the current drain on fuse 20 problems. I'm hoping they're related. I'll post back if I find anything.

In my car, I have a strange phenomenon where my dash illumination will come on while I'm driving down the road (as if I turned on my parking/headlights). Additionally, when this happens, if I actually turn my headlights on and then turn the key off/remove the key, the car continues to run until I shut the headlight switch off!

Also interesting, is that if I pop the hood (with the car 'running' on the parking light switch), the car instantly stalls when the hood light comes on.

Once upon a time I thought that my cigar lighter illumination was shorting to a on-while running wire, but a few weeks later it surfaced again.

I too had the same issue with the instrument cluster beeping, scrambling the displays, failure to remember trip odometer, and occasionally rebooting while cruising down the road (and the "fasten seat belt" reminder). Changing the caps in the cluster resolved that issue.

One of these days I'll tear back in to it, but I suspect some piece of electronics acting up somewhere. It is a 'soft' short, because the additional load of the hood light kills the engine when triggered.

**legoman67** · 01-11-2014, 08:58 PM

Im having a very similar problem in a 89 750 as well, the power windows are also always powered up even with the key out(switch is illuminated and windows work).

**shogun** · 01-12-2014, 05:58 AM

But do the lights go off when you lock the car? That is normal

**ivo1st** · 01-25-2014, 09:52 AM

Hello friends.

I have a little update on this problem. I opened LKM and resoldered all of the relays, cleaned the contacts with contact cleaner and with very fine sandpaper. I did the same with all of the relays in the engine compartment.

I resoldered all the relays which are soldered on a little circuit board.

PS. I am not sure whether I did actually fix it but after this procedure I did not see the problem anymore.