Amp meter shows overcharging

72 Swinger /6. Recently the alterator has been over charging. First it would just do it when the car was first started and then go to normal and now its been getting progressively worse. at idle its fine but as you give it gas it climbs. the alt. looks fairly new and I have done nothing to the car electric wise. I have almost 5000 miles on it since I got it, now 46000 org. miles. Please put the responses in idiot terms since electrical things are my Achilles heel (oh yea, spelling too!)