We have an '89 7.3L (<65,000 miles) that wouldn't start the other day because the bateries were run down. It has two batteries, only a few months old. My husband hooked up the battery charger, of course, and proceeded to look at the belts. He found the alternator one was loose and obviously worn. He used the volt meter on the alternator and found it was putting out only about 8 volts -- needs to be at least 13. He would like to use the volt meter on the voltage regulator, but a quick look didn't turn up the location. We need the truck as we are building a house ourselves, but it has been pouring down rain here in western Washington and he is sick, so we haven't spent time working on the truck (or the house). If someone could pinpoint the location of the voltage regulator, it would make it a quick job to check the output. Then we'd have more info before we just start buying parts. Thanks a lot! -Carol

 

located on the right hand fender apron

 

Found it! Putting out 13.6. New belt will fix. Thanks!!!!!!