10-19-2011, 05:10 PM
Join Date: Sep 2006
Total Cats: 11
'96 Tach - Just doesn't work
I've searched and read, but haven't found the answer to an issue I've had for a while. At this point it isn't so much an issue as something that I'd like to fix and understand.
My OEM tach doesn't work properly.
The shift light that is connected to the back of my gauge cluster does work, all the time.
My ECU has a "tach sweep" feature that sweeps the stock tach needle at startup - and the sweep works.
With the engine running, the tach is dead (stays at 0), but the shift light (with integrated digital tach) works perfectly.
The car & wiring harness are 1996.
I'm running Toyota COPs (though I don't think it is relevant)
Vi-PEC ECU (Link G4 Extreme)
...and here's the very strange part. The tach startd working all on its own the other day. Later that day I realized that the alternator wasn't putting out any voltage. I replaced the alternator, and now the tach is back to not working while the engine is running. I've disconnected the alternator a few times and get the same results:
With car running & alternator working (~14.3 volts), the stock tach does not work but everything else does.
With car running and alternator disconnected (~12.5 volts), everything works, including the stock tach.
So, any help on:
B. How do I 'fix' it?