I have a 1990 Ford f800 instrument working on at work and I'm stumped. I got the job after two other mechanics gave up. The alternator is not charging. They sent it out tested good. Replaced voltage regulator still not charging. I checked the ignition switch all good any ideas? Oh and a brand new battery. Also the fashion lights keep blowing the fuse . I checked everything I can think of head light switch wiring under dash all lights . This thing is not making any sense so I'm breaking down and asking for help. Thanks in advance. And feel free to say dumb a@$ if I have missed the obvious

 

What are fashion lights? Google lead me to funny looking house lights or the runway for the ladies.
Disconnect what ever lights those are and see if the alt. charges without the fuse blown.
Have a wiring diagram? What is the serial number? A little sceptical to answer without knowing exactly what you have but 12V to the field on regulator should put the alt. at full tilt. That eliminates some things.

 

Checked all your other fuses? On my 1991 it quits charging if one of the fuses under the dash blows. First time it did it it drove me nuts. Alternator tested good and everything else worked. New fuse and I was good to go.

 

I'm sorry for the not getting back to this post got side tracked off that truck at work. As for the fashion lights? That is a typo meant dash lights sorry about that. I didn't get the truck fixed. Some time in the past someone changed the plug for the voltage regulator and cut the I wire off the plug. How it ever charged us beyond me. Changed the plug ran a switch hot wire to it and the alternator charges great. As for the fashion lights. Short story the owner of the truck did some repairs some how he won't admit how. He took the wire for the radio light dimmer which is tied in to the fashion lights. And grounded it. Because it was a black wire. I told him about it he said it was black had to be ground he thought.That took a while to find. Thank you guys for the input I didn't follow it

 

Damn auto correct. I did follow your guys input disregard the didn't follow sorry for fat fingers