I had the engine replaced in my 78 F250 and now the alternator guage keeps danceing over toward charge while I am going down the road and if I turn on the a/c and headlights it dances even more toward charge. when the truck idles it goes over to the middle where it should be. It cranks and runs fine and I checked everything I know to check. The only thing I see wrong is that the connector on the RFI capacitor is burnt into. Can anybody tell me what it's for and is that what my problem is?

 

The capacitor filters out high-frequency noise caused by the ignition so that it doesn't get into the radio. It's not related to your problem. I would test the alternator and regulator at a parts store (I know Autozone does both).

 

Since the engine was just replaced, I would check the small ground straps that go from the engine to the firewall and any other small grounds that may have been forgotten, or may have too much new paint under them.