Yup. REAL common problem. Unplug the small connector on the side of the generator and you'll see the flickering stop. Start by replacing the battery. Plug the generator back in and try it. If they're still flickering, replace the generator.
There's no polite way to say it; GM went from the second best generator to the world's worst pile beginning with the '87 models. Due to their design, they develop huge voltage spikes that interfere with computer sensor signals, and they can destroy the diodes and internal voltage regulator. It is real common to go through four to six generators in the life of the vehicle.
What many professionals are finding out is to reduce the number of repeat failures, replace the perfectly good battery at the same time. As they age, they lose their ability to dampen and absorb those spikes. The battery will work fine in an '86 or older car. You might get lucky and not have any damage yet to the generator. That's why I'm recommending replacing just the battery first.
Thursday, July 14th, 2011 AT 7:49 PM