Battery Light, 2000 F150, 4x2, V6

[skin052]

First of all thanks in advance for any help, here's the story. A few days ago my battery light came on and went off randomly. Still started and ran fine however last night when returning home I noticed the battery level dropping until the radio and lights started to flicker. When I hit the gas the gauge shot up to normal, got home and shut it off. Started it again immediately and it barely started. Tried again this morning and of course no go. I figured it was the battery or the Alternator so I removed both. I got the alternator tested and was told it was good to go. The battery was reading 11.5 volts but slowly trickled down when reading the Ohm meter. I bought a new battery and installed the old alternator. Truck started but battery light is still on. Gauge reads normal. So what to check next? Lastly, I am no mechanic by any any means but handy with tools and can follow directions, somewhat. So any advice I get will in turn cause me to look through my Haynes manual to find the parts, lol. The truck is old enough that it pains me to throw allot of money into for expensive labor and parts. I am willing to tinker with and hopefully someone here is willing to guide me in the right direction. Thanks.

 

[Kevsha]

where did you have the alternator checked, because it sounds like its bad.

with the truck running put the DVOHM across the battery terminal, whats the volt reading you get? if it less than about 14 volts than the alternator is not charging. though they say the acceptible amount is 13-15 volts itshouldn't be too far lower than 14 unless you have alot of electronics running

check fuse no. 11 (20 amp) in the battery junction box and fuse 30 (30 amp) in the central junction box, if either are blown that could be your problem

if they are on and its not charging then measure voltage at the B+ wire at the alternator (the big wire held on with the nut) you should see battery voltage

if ok then remove the 3-pin connector and measure the VOLTAGE between pin "A" on connector side (the pin closest to the B+ should be a orange/light blue wire) and ground should be battery voltage.

connect the 3 pin conector and turn the ignition to the "run" position and measure voltage between terminal "I" (Light green/red wire at the opposite end of connector as "A") by backprobing the connector. this van be done with a thin metal pick if you don't have a backprobe tool kit. you should see voltage there.

the next two tests the results will end in with either raplacing the alternator or the regulator and since a new alternator should come with a regulator, you need an alternator if the results of the above tests are as written.

 

[skin052]

Wow, loads of info there. I just checked the truck in the off position and got 12.30, turned the truck on and got 12.07. Obviously thier is a problem, I just want to confirm it is the Alternator and not something else.

check fuse no. 11 (20 amp) in the battery junction box and fuse 30 (30 amp) in the central junction box, if either are blown that could be your problem. Battery junction box is located on the Firewall near the battery and central box is under the dash, right?

if they are on and its not charging then measure voltage at the B+ wire at the alternator (the big wire held on with the nut) you should see battery voltage Check it to where? Between it and the negitive on the Battery?
if ok then remove the 3-pin connector and measure the VOLTAGE between pin "A" on connector side (the pin closest to the B+ should be a orange/light blue wire) and ground should be battery voltage. The 3 pin connector going to the Alternator, right?
connect the 3 pin conector and turn the ignition to the "run" position and measure voltage between terminal "I" (Light green/red wire at the opposite end of connector as "A") by backprobing the connector. this van be done with a thin metal pick if you don't have a backprobe tool kit. you should see voltage there. Nope, completly lost me on that one. But thanks so much, now I have a few test to try.

 

[Kevsha]

check fuse no. 11 (20 amp) in the battery junction box and fuse 30 (30 amp) in the central junction box, if either are blown that could be your problem. Battery junction box is located on the Firewall near the battery and central box is under the dash, right?

Tbattery junction box is under the hood, the central is in the truck

Check it to where? Between it and the negitive on the Battery?
yes, or another good ground

The 3 pin connector going to the Alternator, right?
yes

Nope, completly lost me on that one. But thanks so much, now I have a few test to try.

lol, no problem. even if you can't do that test more than likely it needs an alternator. a re-built alternator from ford (130 amp) is $220.47 list price. you can probalby find cheaper in the aftermarket

 

[skin052]

I will try and do all these checks tonight if I have time before Salmon fishing that is. Haynes Manual refers to checking a Alternator feild fuse? Where would that be?

 

[Kevsha]

that would be the 20A fuse number 11 under the hood

 

[skin052]

So, I checked both fuses and both are good to go. Checked between the big lug on the alternator and battery - and got battery power, good to go. I even checked voltage at the starter relay and got battery power. Checked the 3 pin connector as suggested and all was well although it doesn't seem to want to clip in properly and I can just pull it out if I tug hard enough, I am confident it is making a connection though. I looked for loose wires, excessive corrosion, etc but nothing seems obviously wrong. When I went for a run tonight I turned on the head lights and noticed the battery gauge drop immediately! I am off to get a new/rebuilt Alternator and serpentine belt tomorrow. And maybe I will punch that Parts guy right in the throat for telling me my alternator was fine, I have to admit the thing looks like a piece of crap but I was told it was fine so what do I know?

Excellent advice by the way, just what I needed to point me in the right direction. I am not mechanically challenged, just a little lost is all. I will update tomorrow.

 

[skin052]

Another thought, can i just work the belt off over the fan or do I need to remove the fan?

 

[skin052]

Looks as though I can work the belt off over the fan. Hopefully!

 

[Kevsha]

you shoudn't need to work it off the fan, you need a wrench to move the tensioner. i think the 4.2 its a 3/8 adapter.... but i could be wrong

 

[skin052]

You are correct, I just looked again and it does not need to go over the fan. I will be replacing the Alternator and Belt tonight, more to follow.

 

[skin052]

Damn it all to hell!!! Took it all apart, alternator off, belt off and I don't have a 15/16th socket or box end wrench to get the pulley nut off!!!

 

[Fellro]

You may not have to worry about the pulley, many come with the pulleys on them. Otherwise, it is easier and faster to use an impact to get the nut off... we do it all the time at the store.

 

[skin052]

Nope, no pulley. I should have known since I removed it a few years back with help from a friend who had a ton of tools. He was a Aircraft Mechanic. I forgot how difficult that thing is to get off. The only way I see to do it is to jam a screwdriver into the side of the alternator to stop the spinning and crank on it with a wrench. I may have an impact set at work.

 

[skin052]

So...........................I hitched a ride to work with a buddy and took the old alternator to work and took off the nut with an impact wrench. We picked up a couple cases of beer on the way home and tackled the job. The new alternator and belt were on within 2 beer!!!! Started the truck and still have a battery light!!!! Tested the battery, 12.2V turned on the truck, 11.5V!!!!!!! Cursed and stomped for a bit and realized that we forgot to hook any wires into the Alternator!!! Plugged her in and all was good, finished the beer and felt proud!!! Thanks for all the help!!!

 

[Kevsha]

no problem, i figured it would be an alternator from the begining. go smack the guy that told you it was good.