Hey all, I just installed a 2-1/16" "mini-tach" in my 73 std. beetle today.
Light works, and dims with the speedo light, it's installed great in my little custom maple dash panel....the only prob is that it seems to be reading about 50% of what it should. I get about 500RPM at idle, and like 1700RPM at 60 MPH. No matter how high I rev the engine, it won't tach past about 2500....
I have triple checked that the little dip switches are in the correct order for a 4 cylinder engine. I also tried 6 and 8 cylinder setup, but that only slowed the reading more.
My question is that the tach is getting it's signal from the negative side of the coil, but the distributor in VW engines turn at half the engine speed, so could that be sending a false signal (50% of what it shouold be)?
Is there a way to hook it up to the alternator? The instructions show how, using an "A/C tap" but I don't know what this is, or if my alternator has it.
Thanks for any help.
~Anthony