voltage fluctations

I tried two VR and still have the same problem. The one I had charges around 14.5 at high idle. Swapped it out with two differnt ones and the charging is around 13+ volts at high idle but as soon as the fan comes on at ldle it drops to 12 and if I put the lights on it goes down to 11 volts. When I rev the engine it stays the same, it will not come up.
I am at a loss.
Thanks
AL