ok i had an over charging issue a few months back ended up with a new motorcraft alternator and voltage regulator new wiring new battery belt and tenchener. so this mornin i started up my truck for work n headed down the road i noticed my battery light was on i look at the gauge its reading about 10 volts. so i grab the clutch rev the engine and it stays the same. but when the rpms dropped below 2k it went back to normal so i get back up to cruising speed "45mph @ 2100rpm" voltage drops back down so i lower my rpm to 1700 starts charging fine again. so on my way home it didnt matter the rpm it only charging 10 volts so i checked the belt and its tight check all connections all are clean and tight its got me stumped. ever since i put all the new stuff in its been charging fine till today.

 

Your new alternator is defective. Exchange it on warranty if you can.

 

do u think itss the alt or voltage reg bc when i got the alt it didnt have a reg so i was strapped for cash n got a duralast reg and slapped it on. also i was just thinking i put the brushes out of my old alt bc it didnt come with em

 

The brushes are worn out. When the rpm's rise, they no longer make contact.

I have NEVER seen a NEW alternator that didn't come with brushes..........

 

well i checked the brushes they r still good all connections are tight. i took all the wires off the soloniod cleaned them cleaned the battery terminals. still the same

 

Your voltage regulator is bad then.