I HAVE A 1988 MUSTANG GT, HEAD LIGHTS, TAIL LIGHTS, INSTRUMENT PANEL FLICKERS, RADIO SHUTS OFF AND TURNS ON BUT, DOESNT HAPPEN ALL THE TIME, FLICKERS WHEN IT WANTS. NEW BATTERY AND ALTERNATOR. EVERYTIME THE BRAKE IS APPLIED THE BATTERY GAUGE DROPS TO RED.

 

You have an open circuit somewhere close to the alternator is my best guess.Start at the alt and check every connection including ALL grounds.Corrosion can cause the things you write about very easily and remain invisible while doing them.Isolate as many of the effected systems as you can by pulling fuses and then trying to duplicate the problem.Give yourself the better part of a day to run these problems down.STUPID INVISIBLE ELECTRICAL GREMLINS!!!!!