Hey guys

I have a 1998 F150 5.4L that is not charging the battery, at first it was intermittent, some days it would charge, then just stop and kill the battery.

* 2 good batteries, one new, one a year old, both 850 CCA with full charge
both tested and holding above 12.5 volts even after cranking and starting multiple times.

* Alternator was removed and swapped with remanufactured, but both original and remanufactured tested good on the bench at the local auto parts store.

* all fuses are good the 20 amp inline, including both main 175A fuses at the firewall, 12.5v or more going to the alternator main,
cleaned all wires, both positive and negative, and all grounds to engine block and firewall.

* all fuses inside under the dash are good, and again at the engine compartment fuse box over the driver wheel well.

Does anyone know what the single wire that goes to the firewall is, I have 3 wires coming from the alternators regulator plug, and then the heavy positive wire,
of the 3 coming from the regulator, 1 is fed 12v from the main 175a fuse and has its own 20 amp fuse inline, the center wire goes back in to the alternator,
the 3rd goes up to a single plug at the firewall and then is lost inside the wiring harness, should this lead have a reading.

Anything else to look at or test ?

Oh yea this wretched god forsaken pile of twisted sheet metal has a plow on it, while trying to figure out the alternator I must have shorted the plow lights and now have no lights what so ever,
no headlights, tail or running lights, I'm $3.38 away from dousing it with a gallon of gasoline and using it as my 4th of July fireworks

Any help would be greatly appreciated

 

The single lead should go to the instrument panel charge light.
From the charge light to a fuse then to the ignition switch where 12 volts is supplied in start and run positions.
Good luck.

 

Thanks Bluegrass

I traced the wire back to the fuse box to number 19,
fuse was good, and I had 12 volts going to it, but I noticed the fuse
would pull out and press in without much resistance.

Long story short, the previous owner had added an after market power adapter
and had used one of those little power clips that wrap around the fuse leg
and then you insert it back in, well it spread the terminal behind the fuse box
enough where the fuse was no longer making contact.

I opted to not take the fuse box down to squeeze the terminals back,
and just twisted the fuse leg enough to make contact, at least I know where to look next time it acts up.

Oh yea on my 3rd beer I trouble shot my light problem and now have everything working
The power of fermented wheat and barley

 

Good luck.
Just don't drive with to many wheats and barleys under the belt.