Have a 2004 250 super duty extended 6 3/4 cab four wheel drive 5.4 v 8 gas engine. Problem ,three tuff starts yesterday , dead last night, charged this morning it started was driving to dealor to have battery replaced she died before I got there. I ended up putting new battery from auto zone, it started and runs fine ( problem battery light still on ) went back to auto zone they checked startinging system and alternator out put, they said something is wrong. I can get a new alt. from ford ( my broth. price he has auto body shop ) $ 191.00 plus tax Im thinking do the job myself NOT SURE IF it could be something else! Dont want to replace if not necc. any other item that could cause a battery light on dash to come on ? Trying to save some $ , work is slow, suggestions please ?

 

Sounds like alternator to me, not hard to change out at all. I would do it myself.

 

check all your major grounds too.

 

Get a multi-meter and set it volts. When the engine hasn't run for a while, check the voltage on the battery on the posts. Now put the + probe on the big wire on the alternator. It should be the same. If not, you may have a bad connection from alt to battery. Check your ground also.

Start the engine and measure it again on the alternator. It should be about 13.8V. If not, your alt is bad.

 

THANKS guys bringing it in to buddies in am , will have him check wire before installing alt. ( hope they will take it back ) If it is just ground or wire. Any other thoughts ? THANKS again

 

T.T.T BUMp ttt

 

If you want to check for bad connections, you need to look for voltage drops while it's running. Checking voltage when no current is flowing will not reveal anything. With no current flowing, the increased resistance of a bad connection won't show up. V=IxR

 

It was the alternator, had it replaced along with serp. belt, if I still have truck prob. do it myself next time. THANKS FOR HELP !