I have a 2004 Ford F-150 XLT 4.6 motor the dash went dark their idiot light popped on and I lost all power the battery was dead. I put a new alternator on it the idiot light went out and now it's coming on and off on and off I took a voltmeter and it's making 13.9 volt with the idiot light on why is this happening what's the problem and the battery is new what do I do?

 

Our trucks are very picky on which voltage regulator the alternator has in it. A reman Motorcraft has the correct one... not sure what aftermarket ones do. The alt should be pumping out 14+ vdc when operating properly. Double check all your connections for corrosion and security. how old is your battery?