2003 Expedition Check Charge system still on after new alternator

Hi everyone.

I'm almost at my wit's end with this thing LOL. I just got in a brand new alternator and installed it on my 2003 Ford Expedition with a 5.4. The alternator is not charging the battery and there is a power draw instead of a charge. I checked the fuse numbered 106 for the charging system and is not blown in perfectly fine. There is the right amount of current running through the alternator wiring harness power cable going from the battery to the alternator. I think it might have to do with the 3 wire harness that clips into the alternator. It seems that there's a miscommunication between that wiring clip and the alternator and battery. I've gone through many different threads on different forms and have yet to find a diagnosis and solution for this problem. I've had my vehicle down for 2 weeks already and needed up and running ASAP!

Any help would be greatly appreciated

What kind of voltage do you get if you unplug the three wire plug off the alternator ? Should see 13.5-14.0v at the battery. ( Might have to raise the rpms to about 1500 or so ...). Less than 13v with that harness unplugged, and you probably have a defective alternator. Do you have a external battery charger you can recharge the battery with ? What brand of alternator did you install ?

Pull the alternator, and have it bench tested at a local parts store. Don't chase your tail for a possible bad part. What was the reason for the part change in the first place? Report back.

Sent from my N9131 using Tapatalk

Thanks for the reply as guys.

I purchased a new DB Electrical AFD0128 135 Amp Alternator.

We got a consistent 12.4 to 12.6 volts with it running at 2000 RPM. I'm confused because I've never had a new alternator like this not work. We checked all the fuses and we even check the clip going into the alternator from the harness as well as the fusible links and everything else from the battery through the harness to the alternator. All the wiring and fuses are perfectly fine. My friend who is a bit of a better mechanic than myself who help me diagnose said it could be one wire going to the PCM. He couldn't find any other reason that new alternator shouldn't be charging the battery.

And we tested it's with the wiring harness in plug plugged into the alternator not unplugged.

Test it at the battery ( engine running .... ) with the 3-wire plug disconnected from the alternator. If the alternator is working properly you should see a fairly steady 13.5-14.0v at the battery.

2003Expedition said:

Thanks for the reply as guys.

I purchased a new DB Electrical AFD0128 135 Amp Alternator.

We got a consistent 12.4 to 12.6 volts with it running at 2000 RPM. I'm confused because I've never had a new alternator like this not work. We checked all the fuses and we even check the clip going into the alternator from the harness as well as the fusible links and everything else from the battery through the harness to the alternator. All the wiring and fuses are perfectly fine. My friend who is a bit of a better mechanic than myself who help me diagnose said it could be one wire going to the PCM. He couldn't find any other reason that new alternator shouldn't be charging the battery.

Click to expand...

I replaced an alternator (2003Expy) one time that I thought was bad and wasn't. The new one was bad right out of the box. I'm with MrMoose, how did you decide original alternator was bad? Sometimes good parts are replaced and it doesn't fix the original problem but creates one or more new problems.

theres a buncha charging system threads on this Forum, heres one … maybe some ideas
https://www.expeditionforum.com/threads/charging-system-woes.33844/#post-279065

whats this 12.4 to 12.6V is that at the battery when it should be 14 or so?
do turning on the headlights drop voltage?

Hamfisted said:

Test it at the battery with the 3-wire plug disconnected from the alternator. If the alternator is working properly you should see a fairly steady 13.5-14.0v at the battery.

Click to expand...

Agree with Hamfisted.... alt voltage should be between 13.5 - 14.5. Your reading of 12.4 - 12.6 is batt voltage.

Hamfisted said:

Test it at the battery ( engine running .... ) with the 3-wire plug disconnected from the alternator. If the alternator is working properly you should see a fairly steady 13.5-14.0v at the battery.

Click to expand...

Perfect I'm going to test that today the next hour. We didn't do that before we tested it with the wire harness plugged in. A 12.4 voltage and draw from the battery was tested at the battery. The reason why I replace the alternator is because I did the same thing exactly one year ago but was in a pinch so I needed to grab a used alternator from an auto wrecker. For the past 3 to 4 months to check charging system light has been going off and on but for the past two weeks has been on consistent and I've noticed a drop in voltage and charge. So I practically change the alternator before I was without a vehicle.

The check charging system light started coming on in July during the hottest week while I was at the cabin. It was Plus 27 to 30 degrees Celsius for a straight week and my vehicle was baking out in the sun. I don't know if that's correlated with the issue but I'm thinking it maybe as the new alternator has not fixed the issue.

MrSticker said:

I replaced an alternator (2003Expy) one time that I thought was bad and wasn't. The new one was bad right out of the box. I'm with MrMoose, how did you decide original alternator was bad? Sometimes good parts are replaced and it doesn't fix the original problem but creates one or more new problems.

theres a buncha charging system threads on this Forum, heres one … maybe some ideas
https://www.expeditionforum.com/threads/charging-system-woes.33844/#post-279065

whats this 12.4 to 12.6V is that at the battery when it should be 14 or so?
do turning on the headlights drop voltage?

Click to expand...

The reason why I replace the alternator is because I did the same thing exactly one year ago but was in a pinch so I needed to grab a used alternator from an auto wrecker. For the past 3 to 4 months to check charging system light has been going off and on but for the past two weeks has been on consistent and I've noticed a drop in voltage and charge. So I practically change the alternator before I was without a vehicle.

The check charging system light started coming on in July during the hottest week while I was at the cabin. It was Plus 27 to 30 degrees Celsius for a straight week and my vehicle was baking out in the sun. I don't know if that's correlated with the issue but I'm thinking it maybe as the new alternator has not fixed the issue.