Please help Me.."Overcharging"?

I just had the same problem with my car. I have just finished installing a painless wire harness in the entire car. had the voltage reg wired up correctly but it was charging at 15-16 volt at idle and would peg the volt gauge as soon as you rev'd the engine. I couldnt figure it out for the life of me. mine ended up being a grounded brush to the alt, housing. the screw that holds the brush in the housing should have a fiber washer under the head of the bolt. mine didn't. it was grounding out the field and letting the alternator charge at full power.