as it says. i have a 79 gs. for those of you that forgot, i had an incident where i took off and the battery fell into the dizzy. right afterward the tach went to seeing voltage and not converting. finally came to find that the alt was gone. when i took it off, soldering chunks fell out. anywho, in the process of trying to find the culprit i took the regulator to my electrical engineer because he thougt the points inside might be screwy. turned out they were mostly ok but he still used an exacto knife to rub in between then and clean them. so the problem. as i'm sitting at idle, the needle bounces. sometimes yet sometimes not. the engines sounds solid. another thing is that it appeared after tightening the alt i had it to tight and the pulley was wobbling. i have since loosened the alt some an the "blips" aren't near as bad now, more of an annoyance. could i have damaged the alt? should i loosen it up more? not really sure how tight to have it and i don't want to get the high rpm squeal. the only belt missing is the ac. there's my small book.

 

My 85 gs does the same thing. I think it is because of low voltage in low rpm. When I turn on the headlights or add more load to the electrical system, it gets worse. When I bring up the rpms to about 2500 for about 30 secs, it stops. It is probably because the battery is charged better when I do this. Although I know that my trailing ignition (the one the tach reads), is arcing to my leading in the distributor. I know this because when I hooked up the timing light it read fine on leading (yellow mark), but when I hooked it to the trailing, (pink mark) the timing light would flash for the pink and yellow marks. So I figure that means the distributor is arcing. Grab a timing light and try it. See if it does the same thing mine did. That could be it too. Cause if the tach reads off the trailing ignition, and the trailing ignition is arcing, it might cause the tach to do something funny.

 

actually the 79's read the leading. it cuts the trailing spark sometimes for emissions. i'll check the timing thing though. see if i cen't find some bogus happenings.

 

Almost sounds like a near dead battery. ~shrugs~

 

nope, +12.39v.

 

Same happens in my SE. All dates back to when I was trying to get home on the highway and the alternator went to the bad place and my car was running at about 16V for a while. For a while I had odd electrical gremlins (including the bouncing tach) like the interior dash lights flashing with the turn signal and cruise control turning off when using the signals. I regrounded the rear lights to the body and everything but the bouncing tach was fixed. I regrounded the battery in the engine bay, but still the tach issue. I'd love another suggestion.