I have a 1985 ford f150 5.8l Windsor auto that isn't charging while driving I've replaced the alternator, battery, starter relay, and the voltage regulator and replaced most of the wires for them all and it still is not charging and I cannot figure out what it is idk if there's anyone in here that has dealt with a similar problem but any insights would help

 

What's it reading at the battery while running?

 

when it's a full battery it's reading between 12.27 to 12.33 it fluctuates while it's running

 

whats the indication its not charging? inside gauge?

 

when I put a ohm reader on it it stays around 12.30v

 

well if charged at rest, should read 12.6v....so your not far off. If it weren't charging, one would assume its far less that 12v

 

should it go up if I'm in park and Rev it? it was flucuating between 12.27 and 12.33 while at idle and wasn't going up when revving it

 

At that voltage, wouldn't worry, once it gets into the 10's or 11's...then you have an issue.

 

as I drive it slowly dies and drops the battery down to around 6v and kills the truck

 

One of the wires at the alternator supplies battery power to the field coils to start the charging process. Sounds like you don't have that power supply. Might be a fuse. Could also be the fusible link on the main charging wire. Use your meter and check voltage at the alternator plug with the key on. The one that has FLD next to it.

Looking at Ford's wiring scheme for those old alternators it wouldn't be a surprise if the wires were mixed up. The voltage regulator could have wiring problems also. You really need a simple checklist for how to use your meter. You need to check power supplies and grounds at the VR and the alternator.

If you don't see 13.8 to 14.3 volts when the engine is running then you have a problem. Worry now before the battery dies.