'89 instrument cluster driving me crazy

[Phoney36]

I have an '89 325IX. Fuel gauge bounces erratically and speedo works rarely.
Ive read all the posts I can find and here's what I've done so far:

1. Removed cluster and cleaned and tightened nut on back of fuel gauge.
2. Replaced fuel gauge and speedo (someone gave me a spare cluster). New speedo worked great for about 3 weeks then same problem showed up again. Fuel gauge still wonky.
3. Replaced entire cluster with a third known-working cluster...same issues still.
4. Cleaned ground point under dash.
5. Replaced fuses 9 and 10 with known good fuses.
6. PO replaced speed sensor in rear diff.
7. Checked and cleaned plug in speed sensor in rear diff.
8. Checked continuity of speed sensor wire...all good.

It seems that everything on left side of cluster works erratically. Even the left blinker indicator sometimes works (known working bulb). Tach and temp gauge all work just fine as well as fuel economy gauge when speedo works.

Anyone know of electrical gremlins that haunt just the left side of instrument clusters? I'm ready to sit down and cry like a little girl.

Thanks in advance.

[ButtJuice]

That sounds nasty.

Maybe there is some sort of jacked up wiring effecting it? Like an aftermarket headunit or accessories.

[ELVA164]

We have a '90 iX with a bouncy fuel gauge and we've narrowed it down to the sending unit in the tank; no time to check yet though. Maybe check that next?

[Phoney36]

Sending unit was my thought but that wouldn't explain the speedo. There is an aftermarket radio the PO put in and that is my next suspect.


Trying out Tapatalk on my iPad

[mitchlikesbikes]

aftermarket radio is probably the issue. the PO of my car botched an aftermarket radio install and roasted the wiring. and literally NONE of my gauges work at all. fuel gauge bounces, that's it. i'm assuming they're related because the gauge cluster and radio power both come from the same fuse (12)

[Phoney36]

I think I'm going to uninstall the radio this weekend and check for roasted wires, etc... Then find someone to reinstall correctly. I'm not an electrical guy at all.


Trying out Tapatalk on my iPad

[mitchlikesbikes]

i didn't think i was either, but the wiring diagrams on e30 wiki are really helpful. however my car is in a million pieces right now and i'm dreading the thought of sorting out the cluster issues when i put it back together so i don't blame you for taking it to a professional

[Gregs///M]

Here are some suggestions:

-Left side of the cluster (fuel/speedo/odo) are all connected directly to their respective sending units.
-Right side (tach, mpg, temp) are connected to their senders via the SI board.

Most problems on the right side are associated with dead SI board batteries, however since your problems are fuel gauge and speedo, you can rule out the SI board.

Try changing fuse 10, 12, and 21. Do not continue to use the 25 year old fuses, replace them with new.
Also some common issues that cause intermittent operation of those gauges is oxidation on the grounding stud or posts behind the fuel or temp gauge. Clean them with emery cloth or a jewelers file or wire brush.

For the speedo, I have see instances of failing or cracked solder joints on the speedo circuit board or the main cluster circuit board. Reflow the circuit boards with solder to repair the damage. Also check the condition of the connector at the rear differential. The metal could be oxidized leading to poor connection.

Finally, if you continue to have issues that you cannot solve, you can send your cluster to us for repair/restoration. We are capable of repairing any cluster problem and testing it before shipping it back to you. Our repairs are warrantied.

Good luck

https://www.BavRest.com