Turn signal and tach problem

[chanley talon]

Im running in to some strange problems. I Have a misfire first off all. Second when i turn the turn signal on the tach goes up and down with turn signal some time the tach stop all together. The miss is at low rpm and only happens when the car is warmed up? If you have any ideas or have experinced this problem help. thanks. It is all connected im sure of that. Could it be a bad alternator?

 

[luv2rallye]

Measure battery voltage with engine off but headlights on (>11.5V), and then engine on but headlights on (>14V). Low voltage makes strange things happen. Low voltage can be either the alt or a bad battery (which pulls the alt down).