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Discussion Starter · #1 ·
Hello I have a 1990 Bronco XLT with the 5.8 and I’m having problems with my alternator not charging the battery I’m only getting 12v while running and after driving for a bit the battery volts decrease. I replaced the alternator and ground battery cable, and battery still same issue. Then I replaced the harness thinking it would change it but it only made a slight difference but still not enough volts to charge the battery. My battery light is on and doesn’t turn off. If anyone could help me in any way I’m trying to diagnose the issue I’m having, it would be much appreciated.
 

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it is likely a bad ground connection. not the wire itself. clean the ground post and area around the alt ground. and batt
 

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You can also have the alternator bench tested at most auto parts stores to check it's condition.

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As suggested above you can take the alternator to be tested. Another suggestion is verifying there is exciter voltage on the Light Green/Red wire when the ignition switch is in the Run position. Without that voltage the alternator is only an expensive idler pulley.

Basic wiring diagram of a Ford 2G alternator:
 

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Discussion Starter · #7 ·
As suggested above you can take the alternator to be tested. Another suggestion is verifying there is exciter voltage on the Light Green/Red wire when the ignition switch is in the Run position. Without that voltage the alternator is only an expensive idler pulley.

Basic wiring diagram of a Ford 2G alternator:
I will check that right now thank you
 

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Discussion Starter · #8 ·
As suggested above you can take the alternator to be tested. Another suggestion is verifying there is exciter voltage on the Light Green/Red wire when the ignition switch is in the Run position. Without that voltage the alternator is only an expensive idler pulley.

Basic wiring diagram of a Ford 2G alternator:
I’m getting 10.91 v at the green wire
 

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I’m getting 10.91 v at the green wire
That is low, but it is probably a result of the bulb or the shunt resistor. Looking more like a bad alternator. Have it bench tested.
 

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Discussion Starter · #10 ·
Yeah I’m gonna go down to the auto part store and have it tested because I cleaned all the grounds and still not getting anything from the alternator
 
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