Belt squeals when electric fans turn on??? WTH

[Mrturner1]

Kindof a weird problem I'm having now. It happened yesterday and again today after I got done installing power steering parts.

So with the truck idling in PARK the idle rpm is about 750 and seems healthy, revs good and sounds like it's supposed to. I let it warm up to operating temp and then to test it out, I flipped the ON switch for the electric fans. The idle dropped to 450-500rpm, and in an effort to get the rpm back up I gave it a little gas (not revved, just a bump) and the belts squealed. Let off and it went back to 450-500 rpm and I bumped the gas a couple more times, same thing, loud belt squeal. Thought that was really weird because electric fans and belts don't touch at all or run off of each other. So I turned the fans back OFF, idle went back up to 750, and the belts were quiet when I bumped the gas and revved it hard.

This has me totally stumped, and I think it's the cause of yesterday's tuning issue and the studder I felt once while driving into town. I don't understand why the electric fans would make the belt squeak. I do understand the drop in rpm's when I turn the fans on to a point. I'm guessing here but the sudden draw of power that the fans require could cause the rpm to drop?

I'll post a few pics of my setup in case it helps. The alternator is a 140 amp, fairly new. I'm not 100% confident in the PO's wiring job but I've chased down most of his butcherings. Fans are dual Flexalite and draw 30 amps I believe.