Hoaguestang91

Hey I have a 1991 5.0 It loses charge at night when i use my headlights. I dont know why I replaced, alternator, alternator pully, battery cables, optima battery, new starter, disconected radio subs amp. I just dont know could it be the alternator wire harness? or the computer on the back of the alternator that controls the out put? Im not sure please help the car is complete after this and the paint is going on this summer i want it runing good finally

2 kwik

there is no computer on the alt. it's just a regulator..first is the belt slipping? are your battery cable corroded? does your alt light work in the dash?

SoDakStang

Is the car losing charge ie. not starting. If so, take a voltmeter and test the battery to see how much voltage it is losing. If it is only when you use the headlights, chances are it's up there. What type of headlights do you have? If they are the type of headlights that have a seperate relay for angel eyes etc, check there. Basically, start disconnecting things until your voltage loss goes away.

Hoaguestang91

I think it is the wires because i replaced the wires up at the fuse link but i believe its the whole thing anyone know where i can get the whole harness??

will

If you got $ painless wiring, if they don't have one instock they'll make it.

AdderMk2

dont foxes have an external voltage regulator???

might be a good place to start

90GTDan

OK, what is the voltage at the battery with the engine running with no lights? Should be 14.25 or so. If your lights are putting a draw on the battery then the alt is either not putting out enough, or you have a bad connection. The crappy power plug on the alt is notorious for going bad. The alt is internally regulated BTW. Sounds like you kinda took the shotgun approach to trouble shooting, change everything. Sometimes it works, sometimes not. You need to do some trouble shooting now. So give us some voltages wit the car running, no lights and with lights.

hatchdemon89

sounds like a crapy low voltage alt. replace it had the same problem but it happened when i switched to electric fans i went threw the same thing u did get a 130amp or higher trust me