I have a '90 STD hatch, and when I have my headlights and turn signals on at the same time all the lights dim. Same goes for when brake lights are on, all of the lights will dim slightly but return immediately if I remove the other loads. Is this normal for these cars, or should I start checking the ELD and alternator? I haven't had any problems with it starting, and the battery seems to be charging normally. What voltage should I be seeing in the system, and how far is it 'acceptable' for it to drop with everything on (so i can test it)?

 

I would check/clean your grounds.