I have a 1997 GMC Savana 1500 with a 5.7 l I take off the negative terminal and I checked first short it lights up fant with a little flicker but when I hit the brakes or turn on the lights it gets really bright and strong I have pulled every single fuse out of the vehicle and replace with brand new ones and I still have the same problem and when I turn the lights on when I'm trying to drive my brake lights do not change when the lights are on and they are just like brake lights in the back and turns on all three lights where do you think my problem might be but my brake lights work if I don't turn the headlights on
It sounds like a typical grounding problem. Check all grounds, especially the one main ground on the frame under the driver's side door, for corrosion and/or looseness.
Thank you I will check that the fuses had alot of corrosion on them I cleaned all that up to now I'm going to check for bad ground