2003 Expedition Check Charge system still on after new alternator

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Hamfisted

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Have you unplugged the harness (3 wire plug...) and checked the raw voltage output from the alternator at the battery with the engine running yet ?
 
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Have you unplugged the harness (3 wire plug...) and checked the raw voltage output from the alternator at the battery with the engine running yet ?

Yes I have. And there was no change at all. It was measuring at 12. 4

I'm absolutely baffled. We've checked the wire going to the PCM, I even took this new alternator to a specialty shop that tested it and it works 100% fine. I literally can't think of anything else the diagnosis issue.
 
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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.

So we tested that and there was no change. Still only getting around 12 volts. The strange thing I can drive it for 15 to 20 minutes and it'll stay around 12 volts. It should be dropping to 9 but it's not. I haven't driven it more than 15 to 20 minutes cuz I'm afraid it will die on me.

It appears to be floating around 12 volts. It looks like it's an issue with the voltage regulator or the voltage regulator in the PCM. I don't think it's the voltage regulator on the brand new alternator. I just got a test at a shop and it works 100%.

I'm seriously at a loss and have no idea what the hell is wrong with it
 

Hamfisted

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Test it at the alternator connection also, with the 3 plug harness disconnected and engine running at least 1500 rpm. Where did you get the alternator ? It's still suspect. I don't remember if you said you already checked for continuity on the heavy wire from the alternator to the positive post on the battery. Disconnect the negative battery terminal for safety before doing the continuity test though. You should see something like .1-.4 ohm resistance if you have good continuity in that line. If it shows open circuit then the fuse-able link is popped in the line.




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stamp11127

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If anyone has the service manual for the 2003, the workshop section has a description of each of the three wires that connect to the alternator in the plug. I've misplaced my cd for that year but looked at the 2002 - same plug but different color wiring so there may be a difference between years.

I would also make sure the alternator is for a 2003 and not for an older model. RockAuto lists different alternators for the 2002 vs 2003.

Here is the pdf wiring diagram:
Test for 12v at pin 3 - orange/lt blue wire.
 

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1955moose

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On top of what Stamp stated about different year, different part #, the next year 04 lists a different alternator if you have a 5 CD changer/vs not. If you still have original, cross reference old original alternator. Years back I managed an Oreillys, then Kragen, you wouldn't believe the struggles we ran into. Sometimes only having original part numbers got us the right part. See problem is when some knucklehead transfers wrong part # from paper book to digital computer, it's wrong all the way to the end result. Add to that and you have a vehicle from another country sent here, and it gets real fun. Run Vin and be 100 per cent sure your vehicle is 03. 03/04 have the wackiest issues with fuse boxes, EGR problems etc, so the wrong alternator, or wiring is possible. This may be one of the situations where a person of more experience on such a matter, may have to finish your repair. I've done that before, and never gave it a second thought. Like Clint says, man's got to know his limitations! I do.

Sent from my N9131 using Tapatalk
 
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Hey guys. So something strange has been happening since I was forced to drive my vehicle the other day. I started off driving the lights were dim and the voltage Gage was low. I floored it and within 2 seconds of revving the engine fairly High the voltage gauge shot up past the half mark and the fan and lights started working at full capacity. If I drive slow and modestly for while the voltage gauge and everything seems to go down a bit. But if I drive it a little more aggressively and give it a little more throttle here and there the voltage maintains a higher level and everything seems to be fine. The check charging system light still comes on and stays on even after I clear the code on the drive.

Any ideas what could be causing the voltage do shoot up when I drive a little bit harder and for it to go down substantially when I drive around like a grandma?
 

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