MyE28.com

Ok, yes, I have searched through all the forum material. Yes, I've looked at my Bentley (often useless for M5) and shop manuals. Unfortunately, these questions seem answered but all of th ediagrams they reference are long gone because this site won't host any images and image sites die.

I have an E28 M5 project car. Pulled the cluster to replace the dash. Dash is back in. everything else is almost in. Now I have a couple of extra wires with edge connectors and 2 extra bulbs. I know that one wire is the Cruise control and that has three wires on it (blue/yellow, blue/yellow, blue/grey) and is on the left. The other two wires are BOTH solid brown with blue plugs. The cluster has 3 edge connector slots, tagged Grun, Blau and Weiss. OK, one is CC/Tach But the other two? No idea. There was not enough clearance behind the cluster for me to get a useful image before disconnecting things. Anybody out there with an '88 with a stick that can tell me which wires go where?





Then there are the bulbs. I am not in a position to test dash lights because other things going on require the battery to be disconnected. There are 3 empty idiot light holes at the bottom of the instrument panel, 2 of which might apply. One is Anti-lock and the other is Check Engine. Any idea which bulb goes where? I can't really decipher the wire codes (one light is grey and green/white and the other is green and red/grey).

Now, the REALLY funny thing is that I have another pristine E28 M5. I always try to keep a puzzle box cover for my puzzles as a reference....saves a LOT of time. But if I pull the cluster from THAT car to see where the wires go and something disconnects while I'm trying to pull it, I'm screwed.

Suggestions?

OK, since I got no reply, I pulled the cluster form my good M5. Below is what I found. I still have to figure out which of the two brown wires I should connect since neither was connected in my good car.


I'll spell it out here so that when the 3ed party image goes away, the information is still useful.
The grey and green/white bulb wire goes in the left-most lamp position on th ebottom of the cluster.
The edge connector with multiple wires goes in the first (leftmost) edge spot.
The edge connector with the blue/white wire goes in the middle edge slot.
One of the two brown wires goes in the right edge slot.
Note that the edge connectors all "face" into the cluster and the wires feed through the bottom of th esafety cover (if yours is still there.)

I will report back when I figure out which of th ebrown wires plugs into the console. I believe one is for an automatic gearbox and the other is for a manual gearbox but I am not certain which is which.
I also have one extra lamp socket that probably goes to one of th eother items pulled as part of the dash swap.

None of your images work.

Bear with me, this will be one of my lengthier posts, but lots of good info for E28s; for TL;DR folks, just skip to the last photo for what connectors go where.

I've been putting my M5 back together after being in a mostly disassembled state for many years (garaged), and have been tackling getting the instrument cluster cleaned up, installed euro telltale and warning indicators, etc. Of course I neglected to label what went where when I pulled the cluster years ago, so here we are in this thread (among many) I located a very similar post by the OP over on bimmerforums and pulled his images off that site; these are them.








This last photo of his, based on my hours of research on the wiring diagrams and testing with a multimeter, is mostly incorrect. If you hook up the edge connectors how he has listed, the cruise control will not work. There is only one spot on the US spec M5 (and likely later model 535s) that has terminals to hook up the edge connector with the two blue/yellow (Bu/Yl) wire on terminal 2 and the single blue/brown (Bu/Br) wire on terminal 1; this spot on the back of the speedometer is know as connector C8 and it is shown in the photo below. You will also notice, the other sections of circuit board to the left and right of C8 have no terminals, so even if someone plugged one of the other edge connectors in to one of the bare spots, nothing would happen.


Per the BMW wiring diagrams and my testing, the only edge connector that should be plugged into the back of the speedometer is the one for the cruise control, discussed above. However (this is where it gets weird), on my M5 the cruise control edge connector (2 Bu/Yl wires, 1 Bl/Br wire) was factory cable tied to the main harness "trunk" and there was no way in hell it had enough slack to plug into the C8 connector on the back of the speedometer. But when I last drove it (and I've owned the car since 2008, and made two cross country trips), the cruise control worked perfectly and so did the on-board computer (OBC). Also if you look closely at the photo above, only the number 2 pin of C8 showed any wear (or evidence of the edge terminal sliding across creating the parallel striations in the contacts). That's weird. That would mean one of the other three edge terminals with only contacts on the number 2 side must have been plugged in. So I pulled out my multimeter and started checking continuity with the Bu/Yl wires (terminal 2) of the cruise control edge connector. Turns out the edge connector with the single Brown/Red (Br/Rd) wire has direct continuity with the Bu/Yl of the cruise control edge connector. Pin 2 of C8 is the speed signal (see wiring diagrams below), pin 1 is a ground and goes to the cruise enable pin of the cruise control computer. What I can't figure out is how the cruise control worked all these years without it? I thought somehow the cruise control computer must be getting this cruise enable ground signal from a "back door" source, but none of my testing proved that. So that left me wondering what to do? I've ended up cutting the cable tie to release the cruise control edge connector and plugged it in to C8. Per the BMW wiring diagrams this is how it should have been and in a month or so the car should be back on the road and we can test it out.

So to clarify, for the US spec M5 and likely later model 535s, the only connectors that are plugged into the back of the instrument cluster are the large blue, yellow, and white connectors (should be self explanatory ), the ABS warning light (green wire, gray/red wire, bulb), and the cruise control edge connector (2 Bu/Yl wires, 1 Bu/Br wire). Nothing else gets hooked up.

How I found the cruise control edge connector cable tied to the main harness


Cruise control edge connector and Br/Rd edge connector


Wiring diagrams (there are more, but these show most of the important parts)




Final connections (corrected version of OPs photo above)


Standing by for questions or comments.

This was extremely helpful narrative but all the photos are missing. Can you please see if you can post them again? I have the same issue with my e28 m5. Thanks!

I checked the post and my google drive, not sure why it isnt working. All my other posts with photos seem to be working?

Can you possibly email them to me? My address is smoidless@gmail.com. Thank you!

Machtig wrote: Oct 23, 2023 5:13 PM I checked the post and my google drive, not sure why it isnt working. All my other posts with photos seem to be working?

For regular users, you just see the word "image." Try looking at your post via an incognito tab where you haven't logged into Google. I hit "edit" on your post and copied the URL for one, and pasting that gives me a "403 Forbidden."

Shawn D. wrote: Oct 23, 2023 8:41 PM

Machtig wrote: Oct 23, 2023 5:13 PM I checked the post and my google drive, not sure why it isnt working. All my other posts with photos seem to be working?

For regular users, you just see the word "image." Try looking at your post via an incognito tab where you haven't logged into Google. I hit "edit" on your post and copied the URL for one, and pasting that gives me a "403 Forbidden."

You're not wrong Not sure what happened. They worked when I first posted it, and this seems to be my only post with this issue. I'm just going to repost.

Fixed the photos; for how long, who knows?

Thank you!