Hi guys, I just put a new Stewart Warner electric tach in my rod. Its wired up right as far as I know. A feed from the negative side of the coil (not the resistor ballast side) to the signal terminal - a 12v feed from a known live power line and an earth to the body at a point where all the other gauges are earthed. When I switch on the ignition, the needle dips the wrong way and does not go back all the way to zero. When I rev the car it works the tach and the needle moves OK, but it cannot be showing correct readings as it doesn't start at zero. The Stewart Warner info says this is a bad earth. My question is, can the tach work like this with a bad earth? surely it wouldn't work at all? All suggestions gratefully received.
Sounds like the pointer is in the wrong spot on the movement shaft. try a better ground and if thats not it, the pointer is on the shaft incorrectly Mark
Is there an adjusting screw visible anywhere? My VDO tach has to be calibrated and zeroed against a known tach. Like a tach and dwell meter.
No, there's no adjuster. The weird thing is it appears to be showing the correct revs. Just not going to zero when you switch on the ignition. I think I'll live with it. Strange though. Thanks for the advice guys.
This is normal for new style Tachometers. I use Autometers in my units and they all do not read to zero with the key off.
I am having a similar problem. I have checked the wiring and added a designated ground. Also, just installed a new tach filter which actually made the problem worse. The tach now reads at a higher scale now than before. I am running a Mallory Unilite dist. and Mallory coil, SBC. Signal comes from the coil. I have researched quite a bit but can't seem to find the answer. ANY HELP PLEASE!!
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