'01 F-150 electrical problem
 

It all started a while back. I drove it to the store and when I came out and turned the key, it did nothing. No lights, no clicking, nothing. Had it towed home and the tow truck driver took out his jump pack/battery tester kit and it jumped and started. And his kit said the battery wasn't charging. Sounds easy right? Well, just to be safe, I replaced the battery and the alternator. Ever since that day, the voltage intermittently spikes high. The battery meter pegs high. The windshield wipers speed up. The lights flash... etc. Then just goes back to normal. Then spikes again... and back to normal and so on. It seems to do it more often when I step on the gas. Any ideas?

Check the alternator to make sure its not over charging. I had a new one once on my camero that was overcharging and cause similar symptons. Also while your at it check your wires and cables to make sure all tight, no corrision and a good ground.

i would recheck the alternator.i replaced mine and it was overcharging,i had to get another one the first was bad.i had similar syptoms to the ones you describe

make sure the alternator is grounded good, and motor ground to frame strap is not corroded. look at plugins and make sure no corrosion.. then alternator regulator might be problem.