So this truck sat in the garage for a good while and the alternator was charging the battery fine when first put in. So this year i went to get it going again and found out the battery keeps going dead which this is a new battery which i replace the old one which was siting in the truck...

And when checking the voltage when the truck is running it reads ony 12.40.. With everything on lights etc it drops down to 12.01. I tried pulling the native cable off and it stalled right out.. So that tells me usely the alternator is bad.

I had a warranty on it anyways so i went to get a new one and got it and came home and put it in and it has the same problem..

So i changed out the voltage regulator which did nothing... I even tried new starter relay which still had the same problem..

I also found out about the fuse able link by the battery which is the charge cable so i took that off and tested it hooked up to a small battery and that was good.. I also put new cables and also a ground cable also..

So right now im out of ideas...

Also did the wrench test which you put it on back of the alternator and it doesn't stick to it at all... Than i also tested the voltage coming from the back of the alternator and it reads as it does from the battery 12.40v when running.


what else can be the cause of this? This week im going to try and get down to advance trying not to get stop by the cops because its not inspected... So they can put the test on it to see if that says anything.

 

do you get power at the F and S terminals with the key on? also check I wire from ignition switch to voltage regulator.. google: ford g1 alternator wiring
or do a G3 alternator upgrade..easy and well worth it.. google: Ford g3 alternator swap

did the 130amp g3 upgrade on my 88 Ranger.. love it.. strong 14V with all accessories on.

also installing a 130amp G3 in my 77 F150.

 

Just got done testing those on the voltage regulator with my volt meter.

I posted a pic of mine also and the wires because i don't see any letters written on it. But i get voltage threw all of them with the key on.

There's also a plug with nothing plugged in which i don't know why its like that but it has always been like that sense we own the truck sense 1991 but it did go threw like 2 engines sense we owned it this one is the 3rd which was put in 1999 or 2000. So im not sure if they rigged it up like that or what.

But everything was working before we garage it which was around 2008 and than it was started up every once awhile than my dad forgot about it and it sat with the battery in it for a year or 2 which was stone dead. We had to get a new one for it and this when we notice the problem..




And here's another pic of the plug so it does look like this doeisnt have a I plug.. Ony have F A S

 

the green wire with the red stripe is the ignition switch wire. if you are getting power to that wire, and the "F" terminal on the back of the alternator, and power at the B+ you should be working..maybe the alternator is dead..
you can pull the alternator and take it to your local auto parts store and they should be able to bench test it...it is a little bit of a pain, but at least you won't have to worry about getting stopped by the po-po or having the truck die in the middle of the road.

 

Yep im getting voltage threw all the wires from the voltage regulator F A S. But im ony getting voltage at one of terminals in back of the alternator the one with a red big cap pointing to the right of the driver side.

I cant really see what letters are behind there ''' dad put the new alternator in''' So i really not sure what wire is which. But im not getting any voltages on the other plug with a cap on it which is black.



edit Now that i think about it.. When i was testing the wires on back of the alternator the ground wire did feel a bit loose and from looking up the diagram it says it suppose to go to the native battery cable? I don't see a wire there for it. So im wondering if maybe a critter got to it or something. going to check into it first thing in the daytime.

Would a mess up ground cause this issue?

 

it should be grounded by it's attachment to the engine block(mounting bolts)

with the key on, you should be getting power to the field terminal at the back of the alternator, and the B+(battery terminal on back of alt) should be hot all of the time(key on or off)..if you're not getting power to the field terminal, then the alternator is pretty much "turned off"
see: https://www.ford-trucks.com/forums/9...or-wiring.html for diagram.. will give you an idea of the connections.