rpm and consumption tach dead

[revhard7]

Noob - its been a while, my rpm and MPG tach works fine then suddenly they stop working then they work randomly..
a week ago they stopped working completely i tried hittin the thing, checked fuses 10 12 21, checked the batteries they indicated 3.09 volts, i tried to change the whole rpm gauge (had one in an old dashboard, no id if it works..) it still wont work!!so help!!
is my SI board fried?? or should i rechange the gauge??
on monday im gettin an instrument cluster to try i hope this will fix it
another question: can these instrument cluster be swapped directly??
ps: none of the boards looked fried...
thx

[flying_violin]

My car was doing the same thing earlier this year. Swapped fuses, etc., etc. but nothing worked until I decided to fix my reverse light issue that I was also having. I traced the reverse light wiring through the car, and found that under the shift boot, where the wire goes from underneath the car, through the shifter donut thingy, the insulation had worn through and was shorting on the body of the car. I wrapped each wire independently in electrical tape, replaced fuse 10, and then both the cluster AND the reverse lights worked as advertised! Squished two bugs with one fix.

[revhard7]

nice...i will search for bugs..rpm do go bad i tried to swap si board, the rpm still dead but inspection light had come up so reset it..still no rpm, also found this http://www.billswebspace.com/e30tech...plications.pdf
very useful, i will swap the gauge tomorow if didnt work, will swap batteries.

[revhard7]

checked the reverse shit its fine, changed batteries, tried 3 clusters.. didnt work, i tracked the rpm wire its givin 11.59v at idle and while revving it gets down to 2 v at high rpms.. r these voltage signals right?? plz help its frustrating