my voltage drops when at idle or when i use anything like my brakes,windows and lights on my 86.when i raise the rpms the volts go up.
anything i can do to fix this problem????????

Alternator belt may not be tight enough.

Could also be normal. How much voltage drop do you experience when you turn on the headlights? Is the drop momentary or does the voltage keep dropping the more electrical accessories you use?

it keeps dropping. it drops a lot when i use the lights or when im at idle. the belt is tight and new.

Did you have this problem before you put the new belt on?

yes i have had this problem for a while

First I'd try making the belt tighter and see what happens, also check ALL battery and alternator connections for corrosion and tightness before you replace the battery or alternator. I had this problem before and it turned out I didn't have the belt as tight as I thought.

if i put a 100amp alternator on it , do i need to change any thing else? i tried one and every time i hooked up the main red wire the alternator would turn in to a magnet and drain the battery

Before you do anything else, make sure all grounds are making good connections. A poor ground at the alternator is notorious for causing your problem. Try molving that ground strap to a good clean spot on the engine block.

wheres a good spot on the block??????