Hello all,

I'm new to this forum (as this is my first Ford too &#128513 and it's about time to pop my "posting cherry".


So, on to business:

My truck is a 2001 F250 with the 5.4 V8; upon engine starting, the charging system fault light stays on and the battery voltage steadily decreases.


The battery will run the truck for like 45+ minutes on it's own, so I'm not really concerned about having to replace that yet.


I checked fuses, ensured no corrosion at the connections and grounds that I could readily reach (there's not really much corrosion at all anywhere on this thing).. still no charging.


I checked battery voltage with my voltmeter and it was 12.35; then checked voltage between ground and the B+ post at the alternator itself.. 12.35. I assumed bad alternator and did the good ole R&R. Still no charging.


Removed the replacement and had it bench checked. Passed with flying colors. Good point to add here: it's not a reman part, I decided to go with a brand spanking new alt.


So that's basically where I'm at right now, just waiting for it to be tomorrow and less mosquito-y to continue.


I guess my next step is going to be checking the A, I, and S circuits. I don't have an ohmmeter anymore to check resistance, so I'm thinking of installing temporary jumpers one at a time to the I and A pins from the B+ to see if that kicks on the alternator. In an effort to narrow down my suspects. (I believe those two circuits receive 12v. "I" turns on the regulator and the dummy light and "A" is the battery voltage sensor. And "S" I don't remember exactly what it does but I /think/ it gets half of batt voltage and also is the one that makes sure the dummy light goes off once charging begins.. correct me if I'm wrong!)


I guess what id like to know is: Is there any advice or tips beyond that that anyone has to maybe give me a fresh outlook on this friggin headache?


TIA,

Dave.

 

Some things you can try,
there have been problems with the plug that go on to the alt. Make sure there are no problems there.
There are 3 fusible links in that charging system. Two come from the batt + to B+ on alt, (YE/WH) WIRE ,, third, OG/LB to A term on alt.
The "I" term is from Battery Junction Box, Hot in start and run. , LG/RD

Can you verify with a test light or voltmeter that those 3 fusible links are not open ?

Of course I always ask where the alt was purchased. I have yet to have any problems from an alt purchased from Ford, for what it is worth.

 

[QUOTE=SpicyFly;130493]I believe..I THINK..that since I received battery voltage at B+ post (engine off) that there are no opens in the B+ circuit. As far as the fusible link on the A circuit, I'm going to check that today and see if I get batt voltage there and that should eliminate that too.

And I bought it from Ford. I don't usually buy from the manufacturer, but most big electrical components I've found that it's just easier in the long run to bite the bullet and spend the extra cash on the OE part.

Thanks for the advice, I'll have more info as I get back on it today now that it's not raining.

Also:
I guess one of the concerns I have is if the voltage regulator gets it's 12v input from a computer or other [expensive] module or if this truck is old enough that it comes directly from the ignition switch? I can't really find any good wiring diagrams for the 01 just 99 and 00. I ordered a Bentley but it's not in yet

 

If you verify all the checks and it still won't put out anything, we have both been around long enough to know there is something wrong with the alt or the info it is receiving

As stated earlier there were problems with the connections at the plug, and what might have power with the probe is no guarantee power is actually getting to the inside of the alt.

I don't know about the Bentley, but they do have a service dept too , lol.

Does the output from the alt go to a junction block or does it go directly to the battery? I have seen where there was a poor connection at that junction and the alt was getting high resistance thinking the battery did not require further charging.

 

Well, I'm actually an ASE cert. auto mechanic at a shop here in town, I just specialize in European imports. So taking it to the service dept would injure my pride just a tad lmao Anyways, I got her charging now. There was an open in the "A" circuit; not at the fusible link actually but a spot close to the ring terminal that was just mega corroded away. I appreciate your input and help mate 🤟

 

Glad you got it straightened out.
Thanks for the update.