Have a 1994 F-150 Ford 4x4 the Alt gauge needle bounces back and forth when enging is running and when I turn on head lights they flicker on and off also radio light flickers when heD LIGHTS ON

Simply replace the voltage regulator and brush holder assembly on the back of the alternator. The brushes have worn down so much that they are bouncing. Use a Torx 20 bit driver to remove the four screws mounting the voltage regulator/brush holder assembly to the alternator. Insert a paper clip or drill bit to hold the brushes in place during installation. After installation, pull the paper clip or drill bit out. Much cheaper than buying a remanufactured alternator. Disconnect the negative battery cable, prior to beginning work.