Ok I’ll replace the voltage regulator tomorrow if I get a chance

 

if you are only getting 12.7 volts out of the alternator with the small plug unplugged, your alternator i probably bad too.

 

You later said it tested the batteries and cable and they were fine yet your statement above makes no sense. There is no primary and secondary battery. The system is wired in parallel which makes it one big battery. If the two batteries are greatly different in battery voltage under normal working conditions, I would sure think you have a battery or cable issue going on as they should both be within hundreds of a volt the same reading. So how did you check the batteries and cables to determind they were fine?

As far as a wiring diagram a search on the net brings up many. What does the alternator do if you full field it? If your going to the parts store to buy a new regualtor why not take the alternator in and have it tested?

 

No primary and secondary battery. If one of your batteries is bad it will pull down the good one. Always replace batteries as a matched set.

 

I understand where you are coming from and I need to get better at explaining because the problem has kind of shifted and I keep forgetting to add little details. I was using the term primary and secondary battery because only one battery is hooked directly to the starter and the other one is hooked to the other battery, that’s where I was getting primary and secondary from. I understand that they should be the same voltage because they act like one big battery. I forgot to mention that when I checked the cables I replaced one one tightened all the connections and that fixed the difference In voltage between the two batteries. Now the voltages are the same and drop at the same rate. But the alternator is still not charging them. Sorry for the confusion I will try to mention all the little details. And another thing is that these two batteries are pretty much brand new. I know weird things can happen and batteries can go bad fast but I’m pretty confident these batteries are fine

 

thats a good idea I’ll hold off on going to get parts till tomorrow and I’ll bring the alternator in and get them to test it

 

Having worked in the trade for many years I learned not to assume much of anything as it usually came back to bite me in the a@@. That is the reason I try to start at the basics and go from there. Since batteries are the foundation to get things off to a good start that is the first thing that I want to know is good. Reason for charging and load testing. Next step checking cables if there is any indications of issues. Load test starter if needed. In your case it sounds like most of the attention needs to be directed towards the alternator.

First thing I would check is do I have a field circuit to the alternator? Grab your 4 inch cresent, small screw driver, or what ever you have that is metal and touch it to the rear bearing. Will the alternator hold it? If it will you have a field circuit, if not then you an open field circuit. Common causes are wore out brushes, bad wiring, or voltage regulator that is not supplying a signal to the alternator for what ever reason.

At this point is where you need the wiring diagram. If you do not have the electrical system manual then go to the net and do a search on Ford charging systems. The information is out there. When you are checking voltages do not forget the ground side of the circuit. If you would report what your voltages are at the various test points it should not be very hard to tell you what is wrong in your system. However when you say one battery is 13.05 and I charged the other battery up to 12 what does that mean? To me that said I have a dead battery as 12 volts is a discharged battery. It is the little details which become important, especially when trying to solve issues long distance.

If you would give informaiton on what type of test equipment you have access to it would help too. For instance it does little good to ask what cold cranking amps are your batteries capable of if you do not have a way to measure that.

I learned long ago there are two systems of repair. "WAG" or "SWAG" and when you work with electrical systems they run on "SMOKE" except AM/FM radios which run on all magic or fine magic.

WAG stands for wild a@@ guess. SWAG scientific wild a@@ guess. And if you think about the smoke theory most electrical things when they fail you see smoke correct? When you put in a new part you are putting in a little new smoke so it will work again.

Parts changers use wag, good techs use swag. I will leave the smoke up to you to decide.

 

Ok thank you, ya for clarification to start I had 13.05 on the one battery and the other battery would slowly die if I had the truck running, I then tightened connections and replaced one and now both batteries slowly die at the same rate when I have the truck running, I’ll do a bunch of testing and digging into it later throughout the week, thanks for helping

 

You mentioned earlier that you replaced one of the battery cables. What about the other battery cables and the wires between the alternator, voltage regulator and batteries? Got any pics of your setup?

 

Ya I replaced one just because it was old and beat up and I had been meaning to get to it for a while. But all the other ones were good, I used the multimeter and tested the resistance between all the wires/connections and they were all good. No I only have the couple pictures that I sent