View Full Version : Aftermarket Tach problems

08-19-2003, 02:38 PM
I recently installed a complete MSD Ignition system in my 67 Camaro, complete with a MSD 6A box, Blaster 2 coil, and Pro Billet Distributor. Everything works like a champ! The units have been installed about 2 months.

Recently the aftermarket Auto Meter Ultra Lite 10,000 rpm tachometer has begun to "bounce" all over the place, as if it has a bad ground connection. Sometimes it does not register at all. Sometimes is goes all the way over to 10,000 and stays there. I have checked all connections, and they appear to be correct and secure. It did not do this prior to installing the MSD components.

At this point, the tachometer is no longer usable because it is not accurate.

The MSD 6A box is grounded directly to the frame, and not to the battery. The battery is grounded directly to the engine block. Should the box be grounded to the battery? The engine block is not grounded to the chassis.

Any suggestions will be appreciated.

08-19-2003, 05:27 PM
It is strongly recommended that the heavy black have a good ground either from the battery negative or engine block. If you have access to a low scale voltmeter, probe the tach output of the MSD Unit, it should read about 1.5 to 5 volts. Although this is not an accurate test, but will let you know if there is a signal coming out, which more than like the output is good. You may want to try the tach on a regular ignition to see if it still works.