Voltage regulator question
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Post Fiend
Joined: May 2006
Posts: 10,007
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From: Central Florida
Voltage regulator question
I have the 2002 F250 in my garage, 5.4L and an upgraded alt. I have either a bad connection on the pigtail or a failing volt reg. Randomly (3 times over 8 trips) the alt has not produced more than 11.8v or at all if my battery is in that great of shape. I back probed the regulator while it wasn't working. On the org/lt blu I think I had battery voltage. On the Grn/red I showed ~2vdc. Either there was a ~10v voltage drop from the bulb being lit or I did have some voltage voltage coming in to it. I can't remember what each did. I suspect the battery voltage wire was reference voltage for the regulator and the one with 2v was the wire for the field charge. If that's the case, then the coil is not getting to ground or getting enough power to energize. How can I test this through without putting it on the advance auto tester?
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Joined: Jan 2001
Posts: 56,992
Likes: 2,741
From: Virginia
Here's a diagram of your system.
http://www.autozone.com/autozone/rep...System%20(2002)
If you had 2v on the green/red, then yes that is from the voltage drop of the bulb. That's the way it works. The bulb is fed voltage from both sides. If everything is ok, then it has 12v from the keyswitch on one side, and 12v from the regulator on the other side. That means 0v across the bulb, so it does not light. Sounds like there is a internal problem with your alternator. It's not charging, so it's not putting 12v on the grn/red, so that is making the light come on.
http://www.autozone.com/autozone/rep...System%20(2002)
If you had 2v on the green/red, then yes that is from the voltage drop of the bulb. That's the way it works. The bulb is fed voltage from both sides. If everything is ok, then it has 12v from the keyswitch on one side, and 12v from the regulator on the other side. That means 0v across the bulb, so it does not light. Sounds like there is a internal problem with your alternator. It's not charging, so it's not putting 12v on the grn/red, so that is making the light come on.
