On my 71 f100, it seems like i have an electrical surge. It only happens after the truck has been running for a few minutes. I'll turn the headlights on, and the whole electrical system seems to surge. The lights on my stereo, my dash lights, my dome light. It is bright, then dims a little, and so on. It's not terribly noticable, but if i'm driving down the road sometimes, i can watch my headlights and they are surging. I've replaced the alternator, i've got all new battery cables, and my voltage regulator is fairly new. Any ideas?

 

Jason, there a couple of things to start with...
Replace the headlight switch on the dash. The Reostat may be giving up on ya.
Check the Ground connection at each headlight...
Did you replace the regulator when you replaced the alternator?? Do they match?



__JOHN__Õ¿ö
72 F-250

 

My '70 F100 used to do the same thing. Even though my voltage regulator was fairly new, I replaced it and the surging was gone.

 

How is the condition of the alternator belt? It could be slipping and causing the surging. Check it for the correct tension, you should only be able to deflect it about 1/2 inch inbetween the pulleys. Also ensure it isnt cracked or glazed.

Sparky