I have a 1998 XLT with a 4.6, and 301,000 miles on her. After replacing the head gaskets, I have a weird charging problem. On trips 20 miles or so the battery Guage goes to the bottom line, and the only time it charges is when I take my foot off the gas pedal or when I punch it. Around town I have no issues at all . it charges in traffic just fine. I’ve searched and searched and can’t seem to find a problem like that. Any thoughts suggestions or info would greatly be appreciated.

 

With the engine running at idle (after the dash gague goes to zero) use a multi meter set on 20v and see what the alternator is producing first off. That will at least tell you if you are getting power to the battery.

Have you checked fuses yet? How old is the battery?

 

Thanks for the quick reply, I’ve checked the mega fuses and the battery is 3 months old.