I have a 2003 F250 and I have not had much problems with it just recently my altenator went out on me and I had to drive the truck about 60 miles on just the batteries. When I got it home I put a new altenator in and now it runs good but it is running 1000 rpms higher than it should be. It usually would run 65 mph at 1800 rpms now 65 mph and its at 2800 rpms. I have no ideas. Can any one help?

Here's what I would try:

. Remove and fully charge the battery. Most auto parts stores will do this for free. Don't put the strain on your new alternator.

. Disconnect the negative battery cable and clean the connectors to the mega fuse alternator cable with abrasive cloth. Afterwards, apply dielectric cable. Corrosion likes to develop, here. Also, clean the main negative ground and battery cable and terminal connections.

The PCM is likely directing the engine and alternator (FR Signal) to run faster, in order to charge the drained battery. I know, for a fact, the PCM has this control over idle speed. The PCM compares the electrical load (ELD) signal with the FR (Charging Rate) signal from the alternator and uses that information to set the idle speed and turn the alternator on and off.

Thank you for your sugestion. After I installed the new altenator I did charge the batteries fully before I hooked them back up. I had to replace one of them. I guess I ruined it.