Lights Dim when Brakes applied

Hi anyone experience that when you step on the brakes at night your interior lights and headlights dim a little, and when u step on the gas they brigthten back up? could this be a battery or alternator issue?

I have a 96 aurora with about 97k miles.

thanks

Check the Battery voltage with the engine off and on. Should be around 12.5 and 14. If not get the charging system checked. I beleive Autozone will do it for free. With the headlights and dash lights dimming at the same time, I would suspect the battery first. If it's the original battery, it's given good service. Alternator next. Another possibility is a low idle rpm, if you do a lot of stop and go, won't let the alternator keep the battery charged.