My fault, I told you it was a 4ga instead of 6ga. I'm in hyper mode at the farm right now and my brain is fried. 4ga is the layover wire I often recommend for larger alternators.

Ford states that up to 15v is OK, but 15.4v is higher than that and I've never seen an OE alternator above 14.4v. Mine will go tp 14.5v, but its aftermarket 230a. Voltage is regulated internally in the alternator. The only thing the 'I' wire does is provide a path to the alternator to turn on, by means of a positive voltage (battery post, drivers side). The light will come on to a varying intensity based on the voltage differential between the cluster source (battery post) and the alternator.

Voltage control, though, is from the alternators voltage regulator. It does not use the cluster wire (I) for voltage sense, to know if more current should be outputted. The other wire that is constant battery voltage is the "sense" wire or "A" circuit. What voltage it is tells the voltage regulator to increase or decrease amps. More amps, higher voltage.

Where did you get this new alternator from? There are different voltage regulators, with different set points. It could be a "sense" wire issue, but usually alternator.




Voltage will be low while the glow plugs are on.




We both have '03s, but my harness is a little different, no braiding. I don't ever remember seeing that braiding on anyones OE harness there. The other day I brought back from the farm my original harness, so I just removed the sleeving over the same end you show. It is a little different, but that could be a production change.





If there is any funkiness to the sense wire circuit, the wire out of the two-pin connector could go directly to the alternator output post to sort things out.

Late for bed again....so signing out.

 

The alternator i got is a napa brand, Napa is the only auto parts in the little town we live in. After the high readings i got last night i figured it had a bad voltage regulator, I stopped by napa on my way home and they gave me another one to try, I also picked up one of the in cab voltage meters. Before swapping alternators i figured i would see what the in cab meter had to say. Started the truck, everything seems perfect, truck started right up, volt meter started off at around 12volts, after glow plug cycle it started climbing and leveled off right at 14.3 volts. After about 3 minutes, Bam, battery light comes back on. no change at all in volt meter as seen below

Tested the alternator with multimeter at same time, Multimeter reads 13.17

Now even more confused than ever i turn the truck off. Test the passenger battery and it reads 9.6. I know for sure this is not correct, test driver battery 12.9, retest passenger battery, 12.9. Test alternator wire, 10.6, retest driver battery 10.6. I am pretty sure my multimeter is shot which could have been a huge part of the problem all along, however i still cannot figure why the battery light comes on minutes after the truck is started. I am working about 1.5 miles from home tomorrow so i am going to drive the truck, one of my employees is going to bring there multimeter and will see what his reads

 

Good idea. A funky mutimeter can have you chasing your tail. Right now, I'd trust that power port meter more. I've got 5 meters that can measure voltage, two are Flukes. Occasionally I cross check them.

If the voltage output tracks like it should, you are down to either the cluster has an issue, or the alternator has an issue. If the gauges, dome light, and radio get screwy again, more likely a cluster issue. Taking NAPA up on the alternator exchange is on the table, too. But if the installed one is good, I'm not sure you want to another three-card monte.

But I’d still not rule out a flaky sense wire.

I'll be traveling the next few days, and then again next week, but others here can jump in and help if I'm spotty.

 

Too Many Toys thank you for all your help, I am going to go through your video on the grounds this weekend

Safe travels

Jayme