MyE28.com

Hey y'all,

I'm in the process of baselining an '84 528e auto, and am banging my head against some issues. I recently had a random stall/no-start, and jumped the anti-theft at the OBC computer. I'm pouring over the ETM and swapping around bits and pieces trying to figure it out. The issues are as follows:

1. Speedo fluttered a bit for a couple days and quit completely while driving. No more speedo or mpg gauge.

2. OBC (early) is super on the fritz. Random flickering of cells, seems to be cycling on and off really fast, can't access any functions. Temp gong sounds randomly.

3. Outside temp warning gong randomly dinging.

4. (New cluster) vibrating tach needle w/ticking.

Some troubleshooting I've done:

I checked that the sensor was in place and undamaged. I have read that they don't often fail, so I haven't expended that energy yet. The car has a super eta tach installed, not sure why. I'll check to see if it has an aftermarket chip installed. I got my hands on a new cluster and ECU, with the proper early eta 4500 amp tach. The cluster is different from the one in the car (A separate panel/insert for the tach, different coding plug socket. I've seen this before, but am unsure of the significance). I installed the new cluster (which, by the way has a plastic plug installed where I presume the coding plug should go, or at least I have seen in the past. Speedo still non-op, but the tach is clicking in an even rhythm and the needle is vibrating very fast. Not fluctuating, but vibrating in a way that I would describe as a fine not coarse vibration. Strange. I unplugged the OBC, no change in any behavior.

Things I'm going to do next: Swap out the ECU just in case, and check what we have for a chip. Get really frustrated and sweaty swapping components around and probably cursing a lot. Pulling the speed sensor from my old car and trying that.

Any and all insight very much welcome, thank you as always!

Dug a little deeper here, seems the 1984 car has a late cluster in it, I would guess out of a super eta b/c of the tach. That would be cool if I still had my EAT chip. The spare cluster I got is the correct early type with the low redline. I’d like to use this one, but need to figure out the clicking/needle vibration. I’m going to pull and try a spare speed sender this weekend, and hopefully know how fast I’m going by Monday.

Check fuse 12 for the speedo.

Fuse 12 is good. I swapped in a known good speed sender and the speedo is back in action. Apparently they do go bad.

Here's a video of the ticking vibrating tach:
https://www.dropbox.com/s/z2l76slgnkpov ... 6.mov?dl=0

Is the engine vibrating to the same frequency? Pull the cluster out of the dash and support it with your hands. Does it still vibrate?

It could be buzzing in sync with rpm, it seems to even out over 2000. But it still ticks and vibrates when I am holding it. I’m thinking that maybe the SI board is faulty as the temp gauge just died, and the interval lights keep advancing during a drive.

I should clarify that this behavior doesn’t happen with the 5500 rpm tach that was in previously.

Thanks!

FYI a new used correct cluster fixed these issues.