Resolved Electrical Help Please

[Alabama]

I'm so proud to be part of this group. It is extremely helpful when troubleshooting my foxbody. I am having charging issues with my car. A previous owner did the 3G alternator upgrade on the car. Shortly after I bough the car, I had to replace the alternator because the charging would drop to 8 volts and fluctuate wildly. I bought a new alternator and installed it. It would normally charge at about 14.5-14.9 volts, too much I know. I am now able to start troubleshooting. I followed this thread: https://stangnet.com/mustang-forums/forums/fox-5-0-mustang/ from a while back and have some issues. I have checked all my grounds, cleaned them and now have no resistance between battery and engine block, engine block and chasis. Following the above thread, I have a fully charged battery. When I turn my key on, the battery light and AMP on my dash do light up. I check the green/red wire for 12V and get 0. I opened the wire bundle from the install, the yellow/white wire just comes out of the splice. While re-doing the splice, the yellow/white touched the alternator and sparked. It is a live wire. The white/black just goes from the D shaped plug to the single pole plug on the alternator. Is my car wired improperly? Am I missing something? Thank you for your time. My car is a 1989 Mustang GT 5.0. Mostly stock, no real modifications that I have noticed.

 

[Alabama]

I'm so proud to be part of this group. It is extremely helpful when troubleshooting my foxbody. I am having charging issues with my car. A previous owner did the 3G alternator upgrade on the car. Shortly after I bough the car, I had to replace the alternator because the charging would drop to 8 volts and fluctuate wildly. I bought a new alternator and installed it. It would normally charge at about 14.5-14.9 volts, too much I know. I am now able to start troubleshooting. I followed this thread: https://stangnet.com/mustang-forums/forums/fox-5-0-mustang/ from a while back and have some issues. I have checked all my grounds, cleaned them and now have no resistance between battery and engine block, engine block and chasis. Following the above thread, I have a fully charged battery. When I turn my key on, the battery light and AMP on my dash do light up. I check the green/red wire for 12V and get 0. I opened the wire bundle from the install, the yellow/white wire just comes out of the splice. While re-doing the splice, the yellow/white touched the alternator and sparked. It is a live wire. The white/black just goes from the D shaped plug to the single pole plug on the alternator. Is my car wired improperly? Am I missing something? Thank you for your time. My car is a 1989 Mustang GT 5.0. Mostly stock, no real modifications that I have noticed.

I figured it out (maybe). I did not have the key on to measure the voltage to the green/red at the alternator and the yellow/white is the sensing voltage from the battery (always hot). After noticing the yellow/white, where it was spliced into the car harness, just popped out of the splice, i re-did the splice, everything checks normal. Started my car, voltage immediately sits at 14.5 volts and is rock steady at the battery, 14.5 out of the back of the alternator as well. From what I read here: https://lmr.com/products/Fox-Body-Mustang-Alternator-Guide and other places, 14.5 is within the tolerances for my car with the 3G alternator. Unless you guys come on here and tell me I still have an issue, I'm calling this good. I will leave this up until tomorrow and come back in to put is as resolved. Thank you again for being there.

 

[AeroCoupe]

Mine charges right at 14.4V. The old alternator charged at 14.3 before it died so I’d say you are good.