I just put in a new stereo in my 2001 GMC Sierra. Every once in a while while driving, the dashboard lights up like a christmas tree and the gauges go crazy for a bit then returns to normal. Truck runs fine. I have also noticed on occasion that when I hit the brakes the lights dim a little. Sometimes the truck will do this and sometimes it wont. Alternator gauge is well over 14 volts.Last but not least, if I hit the power window switches "up" and the windows are up, the radio flashes off and on. Any ideas? I bought the 2 wiring harnesses instead of soldering wires together.

 

Got it....turns out to be a loose positive battery cable. Always seem to over analyze the situation. Should have started simple at the start.