chrging system trouble
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Joined: Aug 2008
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chrging system trouble
I'm currently working on a 1974 F250 ranger with a charging issue. The truck keeps running the battery dead in the course of a day of driving. Both the alternator and voltage regulator were recently replaced, but the voltage at the battery won't go above 12.75 no matter how high the RPM's and the alternater dummy light won't turn off. I took the new alternator in to be tested and it checked out alright. I've double checked the ground on the alternator but don't know where the ground is on the VR.
Any suggestions are appreciated.
Any suggestions are appreciated.
Post Fiend
Joined: May 2006
Posts: 10,007
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From: Central Florida
I haven't worked on an external regulator in quite a while, so I might be off. There should be a terminal marked F, this should be the field terminal and have 12volts on it and at the regulator. On my truck when this has a ground the light in the dash comes on, when it's powered properly the light sees 12v and doesn't come on.
Fleet Owner
Joined: Aug 2005
Posts: 23,666
Likes: 301
From: Easton,Ks
I'm currently working on a 1974 F250 ranger with a charging issue. The truck keeps running the battery dead in the course of a day of driving. Both the alternator and voltage regulator were recently replaced, but the voltage at the battery won't go above 12.75 no matter how high the RPM's and the alternater dummy light won't turn off. I took the new alternator in to be tested and it checked out alright. I've double checked the ground on the alternator but don't know where the ground is on the VR.
Any suggestions are appreciated.
Any suggestions are appreciated.
Make sure that what it is bolted to is at ground or run a wire from one of the mounting bolts to the neg post of the battery or a good ground on the engine.
Put a volt meter on the battery and hold a wire from the pos post of the battery to the "F" screw on the regulator or alternator for a very short time.
If the voltage jumps up when you touch the "F" on the alternator but it does not when you touch the "F" on the regulator then you have a bad "F" wire from the regulator to the alternator.
If the voltage jumps up at both places then make sure you have battery voltage at the "A" screw on the regulator and the regulator is grounded.
Wire colors may differ in the following diagram.
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