Why do all my lights dim out at about 4800 rpm and then when it shifts they all go back to bright. Could it be the tensioner leting the belt slip. That is the only thing i can think of. Anybody ever have this happen?

 

I have noticed something like that too. I have an 02 V6 and I notice dimming lights when I down shift they seem to die off and then pick back up, but I have no explaination for why they do this.

 

My lights dim if I put the car in neutral and just coast, as I do when I'm coming into my town.

Thats the only time it happens to me. I assume its just cause the car is only idleing. at about 800-1000 rpm, which means the alt isn't turning as fast, which means its not making as much juice.