My 2003 Ford Expedition

Have you run any test on the charging system? Believe it or not but new parts die. I had a new alternator DOA. Went to all the trouble to install and then had to remove it and try another one. I would take it to a parts house that will put a ODBII on it to see if they find anything

I have an 03 expedition that had the same issue and it was the rear defroster that was the cause. Took my mechanic 3 days of searching to find it. Easiest test is to remove the rear defrost fuse.

If you install an alternator yourself and you have a dead battery, you will almost automatically blow out your diodes in the alternator trying to recharge a dead battery. Charge up the dead battery first with a battery charger, THEN install your new alternator. I've seen this happen too many times before. Also disconnect the battery before hooking up the wires to the new alternator or you can short it out instantly. This may be what happened. Also like another reader mentioned, Rebuilt alternators can be junk from the start. Always buy a remanufactured or brand new alternator, not a cheap rebuilt unit. Many rebuilders only replace the parts that are bad at the time of rebuild so you're basically buying a used alternator with some new parts. Buying new or reman guarantees a completely new inside alternator. Good Luck, Kenny/MrBlueOval

Thank you very much for all your help everyone that has replied to my question.