i have a 69 pontiac gto, and my tach needle bonces all over the place, then fails to work at all, i added a pertronixs points system, with a balster coil, and things were fine for awhile, checked wireing and all seems fine, good ground, ect. added a secound tach and same thing happens! some where in the past i heard about some resister put in the line, also could the voltage regulater have something to do with it? would puting a resister on the voltage reg. help, and if so, what size and where do you put it? how would i find out if voltage reg, is the problem? should i just replace it ? need help please any ideas?