I just picked up a 1990 d250 with 177k on it, the truck has a 727 torqueflite...me and my wife were at the fuel station last night and after I filled up the tank and went to start the truck the engine started up but the wipers went straight up stopped and the left turn signal came on but did not blink, along with the temp sensor pegged, the headlights wouldn't come on, so I wasn't going to sit just a mile from my house at the station, so I pulled around the station and then the lights came back on but the alternator was not charging...I just replaced the battery because the old one was 5 years old and smelled like rotten eggs going down the road and it had a bad cell..the voltage gauge shows to be charging at about 3/4 and that still seems high...what should I look at to try and fix these problems?I just had a left headlight burn out on me Friday morning too..thank you for your help in advance...

 

The alternator is not charging according to the gauge currently...

 

Sounds like a short circuit either in the fuse panel, multifunction switch, or the fusable links.. or even something simple as a bad ground.

Although, you're not going to like this answer, you need to spend an hour or two reading through all of these...

https://www.dieseltruckresource.com/...82&postcount=7

You also need to purchase a mulitmeter to determine voltages, continuity and proper grounds

 

Update...I checked grounds and added.another from the battery to the alternator relay... Actually tried a new relay too....still charging at 18.5 volts from the battery....what next? Just isolate the relay and wire it up to a ground switch?