Electrical Running Voltage Too Low 69 Coupe?

Discussion in 'Classic Mustang Specific Tech' started by 69shocktower, Jul 21, 2013.


  1. 69shocktower

    69shocktower Member

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    Finally got the new alternator installed on the 69 today cause it was so nice out, its still only reading 12.85 on the volt meter while running. Thats after I waited several minutes, it kept creeping up from 12.69 to 12.85 VERY slowly. But that still cant be right. I dont remember it ever reading that low. But that it was the same as the rest of my cars. That their battery reads 12.xx when not running and like 13.75 while running. I cant imagine the starter sylonoid has anything to do with it. The only other component in the mix is the voltage regulator. Im gonna have to search on if how to test it or just order a new one and replace that too. Anyone have any wisdom on this? Thanks
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  2. j69302

    j69302 Active Member

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    Did you have the regulator replaces or checked? You should have close to 14, 13-13.5 and the very minimum, does it increase at 1500-2000 rpm?

    At Idle my stock alt/regulator barely put out about 13.. 1500+ RPMs it puts close to 14.
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  3. daveinmontrose

    daveinmontrose New Member

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    Have you tried full fielding the alternator? can be done at the regulator, by unplugging it, and jumping the "A" terminal(which is battery) to the "F" terminal (which is the alternator field terminal) . Doing this will give you full output of the alternator, and will also test the wire harness in between.
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  4. 69shocktower

    69shocktower Member

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    That A and F terminal thing sounds neat, but i have since put in a new alternator and its doing the same thing so Im gonna focus on the voltage regulator next, see if i can test voltage in front and behind the voltage regulator or just replace the damn thing.
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