I have a 2003 F250, 5.4, with 112,000 miles.

I replaced the battery last August with a genuine Ford battery.

Today when I was idling, the battery light came on. It goes off when I accelerate, but once I let off the gas or the truck is idling, the light comes back on.

I checked the battery and it's connections, all were tight and not corroded.

I put a volt meter on the battery and get 12.4 without the truck running. While it's running, I'm getting 12.03. I don't have a load meter, so I can't check that.

I called Ford and they said it's most likely the alternator. There are two different ones for my truck, but they are $249.03 (ouch).

Does this sound like it's the alternator?

If so, how easy is it for an average joe like myself to change? Looks like two bolts at the bottom and four holding some kind of hold down on top. I'm assuming one of the bottom bolts acts as a pivot to adjust the belt? I see two wires going into the alternator, one looks like a connector and the other has a boot over it, but I'm assuming that just pulls off?

 

Yup!

Alternators aren't hard to replace; attached is from a 2004 shop manual, but the procedure should be the same.

 

Thanks Tom for confirming and also for the attachment.

No I'm a bit confused about step #2, "release the accessory drive belt tension and remove the drive belt from the generator pulley".

I just located the 1/2" drive tensioner, few questions about this:

Can I just use a 1/2" drive socket wrench or do I need a long bar? I put my 1/2" drive socket wrench on there and it does move.

Does this tensioner lock in place or is it just a matter of moving it till the belt can be removed? I think I can move it with one hand and then remove the belt with the other?

If that's the case, then I'm assuming the belt will just stay where I place it and then I can remove the alternator, reinstall the new one, and then get the belt back over?

 

Sounds more like the voltage regulator.....

 

Is there any way to check the voltage regulator?

 

The tensioner is just a big spring loaded arm, move it back with a breaker bar to release the tension and slip the belt off the pulley. Might be a good time to put a new one on. I'd suggest Autozone, Napa or, if you have the time, Rock Auto for a far cheaper and fully warranted alternator. Quick look @ AZ shows a Lifetime duralast reman for $195

 

Yep, my local AZ has one in stock too, same price. Ford could order one in the morning and have it later in the day (if it's at their local warehouse), but their price was $249.03. They mentioned that two were available and they would need my vin number. AZ seems to only have one that's available, not sure if there might be some confusion there?

I don't think I have a breaker bar, but it did move with my 1/2" drive socket wrench, would that be enough for me to muscle it loose with one hand while removing the belt off the alternator pulley?

Beechkid mentioned the voltage regulator. Is there any way to check this or does it sound like the alternator is the culprit?

 

If you go online the procedure is pretty straight forward...and the voltage regular is externally attached to the generator (altenator) .....typically around $50 at NAPA, etc. It decides when the battery will be charged, the generator puts out voltage.....

 

Is there any way to test this?

 

Spend the extra $50 on OEM, box store alts are known to have issues.

You should be able to use a just a rachet to release the tension.

 

Makes sense and that's why I had called Ford first.

I was able to move the tensioner with the ratchet and think it will work without a breaker bar.

So let's make sure I understand this fully, I move the tensioner to release the belt off of the alternator pulley. I then release the tensioner and remove the alternator and replace it. I then move the tension again and apply the belt, done?

I'm going to call the dealer back in the morning to see when they could get one. I think I can handle the job.

 

Here's something weird, just went outside to pull my truck into the driveway for the evening. The battery light is not coming on at all. I'm assuming that the battery being 12.4 not running is fine, but the 12.03 running is the problem.

What should the voltage be with the truck running if the alternator was working properly? I guess dummy lights can't always be accurate?

 

Alternators can go bad and then work again after cooling down temporarily. The brushes go bad on these and you may get an intermittent charging. Don't be fooled, change out the alternator. The regulator is built in the alternator and you are best off changing the complete unit. O Reily's has these a little cheaper but they are re-man's and not the best. If you buy the unit with the forever warranty, you won't buy another, just change it out if it goes bad. I've changed out two after the initial one.

Just a 1/2" breaker bar or ratchet with a helper.

Changing out the alternator is an hour job at best. Sitting on top of the motor and easy to access.

You should be seeing your battery at about 12.8 static. Running you will see around 13.4 volts at the battery, 13.8-14.2 volts at the alternator terminal without resistance loss.

Get a helper on the belt and it's easy to remove.

With over 110k on the belt (if not already changed), replace the belt with a Gates unit for about 50 bucks. Great insurance.

 

I don't know...

I know that most alternators are three-phase, and most often they don't fail all at once. So when one or two of the phases fails it lacks the capacity to power the truck at lower RPMs, which would cause a low voltage concern. But when the RPMs increase that lone functional phase is capable of providing the power demanded by the truck, and the battery light goes off. I've seen this happen more than once.

The one time I replaced a voltage regulator I ended up having to tear the thing apart to replace the alternator, as the regulator replacement didn't fix anything. This was on a Contour, and getting that alternator in and out wasn't a fun job.

Wouldn't a regulator failure most likely cause a high voltage concern?

 

Correct me if I'm wrong here, once I release the tension on the belt, I can then simply remove it, change out the alternator, and reinstall a new belt? Would the tension go back to where it was previously or does that need to be adjusted? If so, how does it get adjusted?

For the tensioner, does it remain in the "open" position after I rotate it with the socket wrench/breaker bar?

I don't have a helper on this one, how realistic is it to do by myself?