Battery or alternator problem?

J.A.G · Oct 5, 2012

Hi guys. I have a 2004 f250 with the 6.0. The other day the battery light began to flicker intermittently. I have a scan-gauge and it said that the voltage was 11.6 volts. The next day I checked the batteries and noticed that the positive leads on the batteries were corroded. before i cleaned them I checked the voltage on the batteries and they both read 11.8 volts. I cleaned the positive post and started the truck. After running for couple of minutes the voltage went up to 13.9 volts. I turned the truck off and checked the voltage on the batteries and both were reading 12 volts. After driving for about 5 miles the battery light began to flicker again intermittently. The scan-gauge showed the voltage at 13.4-13.6 volts. Do I have a bad alternator or batteries?

hawgdoctor · Oct 5, 2012

Sounds kike you have an alternator on the fritz. Get it fixed before it starts killing other high dollar items.
sent from the shop making things fly.....

Atsah · Oct 5, 2012

Check all your grounds and connections before anything. If they are all good, I would say your alternator is on it's way out.

Snake · Oct 5, 2012

Could be either. Have the batteries load checked and the alternator bench tested.

J.A.G · Oct 6, 2012

I had the batteries and alternator tested on the truck and they said that everything was fine. I am going to pull the alternator and have it bench tested. Does anyone have any know of an easy way to release the tension on the belt to remove the alternator? I read that there is a lever on the belt tensioner to release the tension on the belt, but I can't find it.

Snake · Oct 6, 2012

Front of the tensioner pulley has a square hole that a 1/2" ratchet drive fits in. Pull towards the passenger side.

If you pull it far enough, there's a catch on the pulley and tension will stay off the belt. Release the catch to put tension on the belt again.

J.A.G · Oct 6, 2012

I pulled the alternator and had it bench tested and it tested fine. I had the batteries tested on the truck yesterday and they tested fine. I guess I am going to pull the batteries and have them tested again. Is there anything else I should look into?

Atsah · Oct 7, 2012

Atsah said:
Check all your grounds and connections before anything. If they are all good, I would say your alternator is on it's way out.

Did you do this?

Ironhide69802 · Oct 7, 2012

Literally just had this happen on my 05, I replaced batteries cause one was leaking. Light stayed on so I had got a deal on a 200amp alternator. Replaced alternator and all is now well.

Snake · Oct 8, 2012

I had alternator / battery issues earlier this year and started a thread. Some pretty good info is in it:

http://powerstrokearmy.com/forums/showthread.php?t=19277

J.A.G · Oct 10, 2012

That's a great thread. I need to check the grounds on my truck. I will probably do it this weekend. Is it normal for the alternator to get hot? I drove about 20 miles and felt the alternator and it was hot.

F-250-Owner · Oct 10, 2012

are you running any aftermarket accessories? big stereo? amp? try checking the ground on the bottom of the engine by the crank pulley.... that ground wire gets really dirty and needs cleaned along with the stud.

Snake · Oct 10, 2012

The alternator will get hot, not only from "working," but also from engine heat.

J.A.G · Oct 10, 2012

No everything is stock. Would a bad ground cause the alternator to get real hot?

Snake · Oct 10, 2012

It absolutely can, yes.

Lubbockguy1979 · Oct 14, 2012

Mine had a bad voltage regulator. It was over charging. Cooked my batteries. I ended up with a new alternator and 2 new batteries. Not a cheap ordeal.