Stuck Tach

[thealbert]

Hey guys. Quick question.

My tach on my E30 M3 is stuck at 3k rpm when I start and run the car. No matter how I drive, it's always just stuck at 3k rpm. When the car is off, the tach drops to 0, as it normally should. When I start the car, it pops back up to 3k rpm and stays there.

Right before the tach got stuck at 3k rpm, the service light indicators stayed on for a good 1 minute after I started the car. I understand they're normally supposed to turn right off the moment the car starts.

Tried the usual tapping of the cluster and no effect. Wasn't really holding my breath on that fixing the issue, but you never know, it was worth a try. LOL

Would appreciate any insight on where I should start troubleshooting the problem. Is this the common service indicator battery issue? However, when I start my car, the service indicator lights come on normally. Despite the SI lights coming on when starting, could this still mean my SI board batteries need to be replaced? Could it be the entire SI board that needs replacement? Or is the problem a fuse related problem?

Any insights on what could be causing the problem would be greatly appreciated.

Thanks!

[dnguyen1963]

Take the SI board out and check the batteries and corrosion. My guess is that you'll need a new SI board because of corrosion.

[jlevie]

While I won't rule out the SI board as a cause, I think it is more likely that the tachometer is bad.

[thealbert]

New symptom development. Now it looks like my engine temp gauge doesn't immediately work when I start the car. I'll need to run the car a good 5 minutes before the temp gauge starts to work. On a cold morning, normally I would see the temp gauge slowly creep up to it's normal middle position but I've just noticed that doesn't happen anymore. I would stay in the "off"/no temp position and then suddenly pop up to it's normal middle position after starting the car and running it for about 5 minutes. I suppose this is looking more and more like an SI board issue?

[thealbert]

While I won't rule out the SI board as a cause, I think it is more likely that the tachometer is bad.

Wow, the legendary JLevie answering my question! Cool! Thanks for the tip. I've actually purchased a number of stuff from you in the past for my E46. :)

Take the SI board out and check the batteries and corrosion. My guess is that you'll need a new SI board because of corrosion.

Thanks for the tip! My first suspect was also the SI board. Hopefully it's just the batteries and not a corroded board.

[dnguyen1963]

New symptom development. Now it looks like my engine temp gauge doesn't immediately work when I start the car. I'll need to run the car a good 5 minutes before the temp gauge starts to work. On a cold morning, normally I would see the temp gauge slowly creep up to it's normal middle position but I've just noticed that doesn't happen anymore. I would stay in the "off"/no temp position and then suddenly pop up to it's normal middle position after starting the car and running it for about 5 minutes. I suppose this is looking more and more like an SI board issue?

Yes, this is more and more like a bad SI board.

[Cephas]

Ill 3rd SI board. Easy fix

[thealbert]

Thanks for all the inputs and suggestions guys! I was able to fix the problem already. Just thought I'd share the solution. I replaced the SI board. It didn't fix the issue. I then replaced the tach itself. Problem fixed! Looks like it was the tach form the beginning.