I have a 1993 f150 xlt with the 5.0, when i try to start the truck it has to be jumped, and when i get it going the voltage gauge jumps up and down very quickly. I would normally write it off as the gauge if the light under my hood wasnt reacting the same way (flickering), as well as my headlights. when i try to turn on the headlights the truck tries to die but sometimes picks its self back up and stays running (this is a rare happening though). i took my alternator and battery and had them tested, they both passed. im wondering if this may be my voltage regulator? any help would be great and if anyone needs more info from me then just let me know and i'll answer your questions the best i can.

 

I too have a problem kind of like this... 97 F150 4.6 4x4. I can not get power to flow through to the exciter wire. alternator and battery check out fine. checked the resister on the back of the gauge cluster it is fine. no burn spots on the electrical board the resister is mounted on, i have power to fuse 19 but not at the green and red wire at the mega fuse, all 3 fuses are (mega, inline, and fuse box).

with that all said... I ran a jumper wire from the battery top to the alternator at the exciter port. This caused the alternator to start charging. The question is What am i missing? why cant i get the exciter wire to run voltage to the alternator?

 

Clean and tighten ale battery conections or replace bad battery

 

@ bubbabud - If the battery checks out good then would replacing it be unnecessary?

 

Hank the symptoms you describe are clasic signs that the battery is not buffering the voltage while runing and it is runing on the very ragged power of the alternater this is caused by either a bad or completley discharged battery or an open cirquit between the battery and the vehicle or an open cirquit in the battery its self [bad cell conecter]. It could be a bad cable or loose or coroded conection this includes all ground conections. I didnt mean to sound like a smart a** hope you get it sorted out

 

I have a 1993 5.0. It won't start/not even with a jump. Alternator and battery both check fine. Replaced starter solenoid. There is no power at all in the cab. Help!