Just replaced the serpentine belt, idle pulley, and alternator and now my truck is dropping way too low at idle. gauge is going haywire and causing my headlights and other electrical components to wildly fluctuate. I go back to college monday in ramsey nj and i cant be stalling at the intersection by the mahwah police or eastwick. Pretty sure it has something to do with the ignition system but not sure. Kermit has 281,000 miles on him and other than the afore mentioned issue hes pretty much problem free. I cant be playing with my truck trying to get it at a steady idle out of gear every time I stop. I live an hour from my school and sometimes I run a little late. The route I run to school avoids the highway bc I love driving the back roads. The only drawback to this is that I take orange tpke down through tuxedo and i dont get signal on my phone for most of orange tpke so im screwed if something gives out. I got less than a week to diagnose and repair. Not sure if kermit is obdI or obdII either. ready to rip my hair out...

 

I'm not a mechanic, but it sounds like a bad alternator to me. Have it tested at the store. I've seen brand new ones turn out to be junk before. Just my 2 cents, good luck, I feel for you.

 

Check all your fuses and have the new alternator tested.