Tach's dead - cluster swap or SI board?

[91bimmahVA]

My tach stopped working the other day. The light still works and all others gauges work fine.

I have a spare cluster. What should I replace? Can I take the tach unit from the spare and swap it on to the original? Should I swap SI boards? Or replace the batteries in SI board? What would be the best thing to do??

I've searched the board already, but bc I have a spare I wanted to post something to see if I should use the spare or replace the SI batteries/board.

[jlevie]

Can you do an SI reset? If not replace the SI batteries and that will probably fix the tach problem.

[e304lyfe]

it could be any number of problems with the cluster.

the tach could be dead, so could the si board... or possibly the coding plug.

[91bimmahVA]

i guess what im looking for is who's had this problem before and what the easiest, or BEST fix is.

eventually i will do the trouble shooting myself bc i have the spare cluster. im just looking for a chance to fix it right the first time.

by the way, the original cluster has 180k in a 91 318is and is a MotoMeter cluster. the replacement/spare has 140k and is also a MotoMeter but not sure what its from. can a 325i tach go in a 318??

[craig4ie]

Ya my tach is on the fritz right now too, it likes to stick at 2.5k rpm quite often and is getting worse.

bump for more ideas/past experience

[91bimmahVA]

anyone else have any input on this??

[etxxz]

Check a 7.5A fuse that is between positions 18-24 after a 30A fuse...in any event, if none are blown, have the car running/on and tamper/move/push these fuses and see if the RPMS work

had a bad contact problem on mine and got fixed by slightly bending a tab on this 7.5fuse and its all fixed.