View Full Version : Erratic tach with lights on MSD 6AL

Hemi Jack
09-08-2003, 09:35 PM
I recently installed a Mopar Performance branded MSD-6AL. I replaced my MSD-6A to take advantage of the rev-limiter. When I have my lights on the tach is very erratic. The tach is an Autometer that worked well with my MSD-6A. When I am racing the tach is almost unusable as it goes back and forth about 2000 RPM from 1200 to my 6000 redline. When I was racing the car I also noticed a popping from the exhaust at about 5000 RPM. What should I check? I have a 6800 RPM chip in the 6AL and shift right around 6000 RPM. The car has a manual shift automatic. Thanks for the help.

09-09-2003, 10:00 AM
I would recommend checking the voltage at the heavy red and black of the MSD Unit; a low voltage situation will create this type of problem, or even a poor ground. The heavy red and black should be mounted directly to the battery and not to alternator or any other power source. Also check that the block is grounded properly, do not rely on engine mounts or body or even chassis.

Hemi Jack
10-16-2004, 11:32 AM
Just an update on my problem now that the board is back up. It was not the MSD unit causing the problem. The tach ground wire had come loose. It just happened to be at the same time I installed the new box so I thought that was the cause. Thanks for the help msdtech2.

10-18-2004, 10:14 AM
That's nice to know. Thanks for your feedback.