Author Topic: Tach problems (Read 3833 times)

Shift_Now · « **on:** January 04, 2007, 11:15:29 AM »

Since I've owned my car I've had problems with the tach reading incorrectly. at idle it shows 500 RPM, and when the rev limiter is kicking in it shows 4300 RPM, I've replace the whole insturment cluster with a known working one, and still no improvment. Any Suggestions? Has anyone else ever has this problem?

Jimmy Lewis · « **Reply #1 on:** January 04, 2007, 11:42:13 AM »

I have the exact same problem, though I have yet to troubleshoot the issue. The previous owner had replaced the cluster because of a faulty fuel guage. Help would be greatly appreciated as it is quite irritating hitting rev limit at 4500 rpm.

Cristian G in Oz · « **Reply #2 on:** January 04, 2007, 11:05:33 PM »

Check the coding plug on the instrument cluster. It is item number 11.

http://www.realoem.com/bmw/showparts.do?model=AF92&mospid=47256&btnr=62_0064&hg=62&fg=05

There are several different plugs and if you have the wrong this is exactly what it will do. They will provide different readings depending on the different models of car.

I cannot remeber the number of mine but it is the E30 restoration guide. If you want to wait I can put up the number tomorrow.

Jimmy Lewis · « **Reply #3 on:** January 05, 2007, 11:15:04 AM »

I have the original cluster and I'm assuming the previous owner just used a non m42 cluster and didn't transfer this coding plug. I'll swap them out and see what that does. Thanks for the help!

bmwman91 · « **Reply #4 on:** January 05, 2007, 11:26:21 AM »

I have a spare coding plug laying around somewhere. $6 shipped. When I get back in town on monday I can look around for it.

Shift_Now · « **Reply #5 on:** January 06, 2007, 01:32:43 PM »

I have changed tachs, I have changed coating plugs and cleaned all contacts in instrument cluster. Does anybody know where the tach pick up sensor is?

bmwman91 · « **Reply #6 on:** January 06, 2007, 01:44:38 PM »

The tachometer is controlled by the Motronic ECU. It picks up engine speed from the toothed wheel on the crank. If it was messed up, the car would not run at all. If a new coding plug did not help, then I have no idea what it would be...this is a weird problem!