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I have a 1989 E24, and would like to replace the SI batteries of the instrument cluster.
After the instrument cluster was removed I found out that there is no SI board on a '89 E24 as normally found in the earlier models!
There is only one printed circuit board (PCB) underneath the speedo, temperature/fuel meter unit, and the tachometer. I was able to remove the speedo and tachometer but did not know how to remove the temperature/fuel level meter unit to access the PCB. I did not want to use force or pry it up for fear of damaging the unit and/or the PCB.
I did see the 2 batteries soldered underneath the PCB. Please see attached picture.
I would appreciate it very much if anybody who has the same car and instrument cluster arrangements could give me guidance as how to make this SI battery replacement a success.
Nha

Welcome to the forum.... a search will no doubt bring up a bunch of threads. This one is interesting...
viewtopic.php?t=24163&highlight=board I remember a good one on this topic started by Da Hose. Jose is one of the resident gurus *bows* you will come to know if you drop by here frequently.

As always, keep us posted.

I was able to remove the temperature/fuel gauge indicator off the instrument cluster. The unit is bolted to the back of the instrument cluster by (2) 6mm nuts. I was however could not remove the PCB hue to too much resistance.
I did not want to use force.
I wanted to replace the 2 Lithium batteries just for preventive maintenance.
I therefore reinstalled the instrument cluster. Everything works as normal but there is NO DASH LIGHTS!!!
I found a 2-wire (red/gray and brown/white) male connector dangling underneath the dashboard not connected to anything. Please see the attached picture.
The wire colors of this connector are the same as the wires for the 2 light bulbs in the instrument cluster. I found the problem but was unable to determine where this male connector plugs into.
Your help would be greatly appreciated.

You must resize your photos in some type of photo editing software before posting... 800 or 1000 pixels wide for horizontals is good.... 725 for verticals.

Sorry. Here is the resized picture.

Personally, I cannot speak to this but are you familiar with the Bentley manual and the Electrical Troubleshooting Manual? As best I recall the ETM would be of limited help here but it does have some pictures (perhaps the most clear in certain online versions- jpg vs. pdf or something of that sort). There is a sticky in the Tech section with links to these manuals. Please do fill us in on how you resolve this on this thread though!

I have an '86, a '89 E24, and a '92 E34 that all have the same engine so I did buy myself two 5 series Bentley Service Manuals covering from '82 to '95 for these cars.
I found that these manuals do not cover all issues found by the enthusiasts in this forum. Their wealth of experience and expertise is tremendous, and their knowledge had helped me fix things in the past.
I will report once I have fixed the "no dash light" problem.

ntnha2001 wrote:I was however could not remove the PCB hue to too much resistance.
I did not want to use force.

I, too, was frustrated at not being able to separate the board from its housing until I finally noticed the two small screws holding them together.

Thank you for the info. I did not pay attention to these screws therefore was unable to remove the board to replace the batteries. Will do it next time when I get the instrument cluster out again.
I could not find why I lost the dash light and the illumination of the headlight and the fog light knob. I saw a white 2-prong male connector (see picture of the previous post) that has the same color wires of these 2 knob lights. I suspect this connector is supposed to plug into somewhere to provide power to the dash light and those knob lights but I could not find where it is plugged into. Now I cannot drive the car at night because there is no light in the instrument cluster although all othervindicator lights are functioning normally. Any help will be greatly appreciated.

The batteries and the quarter of the panel what holds them was damaged. A guy replaced the batteries and soldered everything what had to be. The car is fully restored, everything was taken apart. I tried the renewed cluster in the car. All the lights worked. The green leds of the service indicator too. A few minutes later the same day those leds stopped working and only came back for just a blink a few days later. The guy mentioned before took the whole cluster and he told me there was a few broken solderings in the other panels too (connected to the leds). I tried the speedo today but no leds. Am i right that when i turn the ignition some of the leds should turn on and when the car starts they go off in a few seconds?

Two main plugs connects to the middle of the cluster. A blue and yellow. There is a small green plug what comes from the same way of the wiring as the blue plug but i can't find it's place. See attachment. Any ideas?

The other thing is my rev counter. After the repair of the battery panel it started working after a few seconds the car started. Now after the second repair it starts with the car but alternates between 0 and 1000 all the time.

Does anyone know what the reddish goop is on the circuit board and how to remove it? I'm changing out my 1990 lithium batteries