RPM gauge confusion

[scumtrash]

i have a 1988 325is and my rpm has been acting really weird. in the past it would blow fuses every couple days. and that went on for about a week, and now it wont work at all. ive gone through and checked the fuses and i could only narrow it down to fuse 10 because the only 2 things in my tach not working are the rpm and mpg meters.

im curious where else i could look to narrow down this issue, the other things on fuse 10 are

Seat belt warning system - the wires were cut when i bought it.

Service interval indicator - this works

Tachometer/fuel economy gauge

Instrument gauges and indicators

Brake warning system -works

Back-up lights - works

OBC- works but the backlight is broken and it is not set

Starter -works

Fuel delivery - works

Idle speed

Active check control

Stop lights- works

cruise control - does not work......

[Gregs///M]

The #10 fuse should be 7.5A. Common wiring faults in the E30 are frayed or damaged insulation for the back up lights near your shifter. Remove the boot and inspect the local wiring for cuts or nicks that could touch chassis ground.

I've also seen the stop lights cause issues. Inspect the wiring harness in the rear of the vehicle, local to the light assemblies, and also check for damaged insulation.

Lastly, the seat belt warning wires are cut already? Those might be the first thing I would check, the ends could be touching ground, although that circuit might be just looking for a dry contact.

[scumtrash]

well thank you, after checking all that today i found nothing so i went though all the fises and found that fuse 24 got me up and running again and then it blew. i started it twice and everything went fine and then the 3rd time the rpm meter didnt work. any idea what that might be?

[Gregs///M]

Fuse 24 is turn and hazard lights. Should not cause the tachometer to fail.

These fuses should be checked with the ignition on and engine off. With a test light, not digital meter or visual check. Honestly, I would just replace them instead of checking them, at least 10, 12 and 21.