Alternator or regulator over charging
 

Greetings , the battery on 70 c20 was completly dead the other day must have left something on , charged it put it back in over night and is holding charge ,now i tested the battery with a volt meter truck running and it’s 15.5 seems high to me could this possibly be the voltage regulator ? Thank you in advance

Re: Alternator or regulator over charging
 

hi my 70 gmc used to charge about 15.5 also. if you have an older external voltage regulator they can be adjusted. google it and learn how. its very easy I,ve done two. you just have to make very small adjustments. I got both of mine down to 14.25 or so. and as the battery charges it comes down even more. maybe 13.8- 14.0 hope this helps. BROWN 70

Re: Alternator or regulator over charging
 

15.5 is in the charging range, but a bit high. Maybe you should shut it off and look to see if something is still draining the battery, or if it is fully charged. A fully charged battery is 12.6V. Minimum charging voltage is 13.5V. Anything below that, you have a charging system problem. Charging at 15.5 seems to me like the system is picking up from a low charge state.

12.6 at battery truck off, no drains. So 15.5 is ok ?
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Re: Alternator or regulator over charging
 

I don't have the CRM on hand but I do have the Chilton's manual, and they are saying 13.8-14.8V. So, higher than it should be. If it has an external regulator, you can adjust the voltage down a little. You'll need a manual for all the steps. Someone was gracious enough to load up the CRM as .pdf files, but I don't have a link.

Thanks for the advice and replies, ill look into adjusting it ,if that doesnt work (or i break it like i usuay do )i want to go with a internal one ..
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Re: Alternator or regulator over charging
 

Electronic regulators are available if the mechanical adjustment doesn't work. I think the model starts w/ VR1 which will get you close.

Re: Alternator or regulator over charging
 

Here's the link you are referencing. Not sure if the regulator adjustment is in there. I made the adjustment on a car about 1973 and recall it is really easy. If I recall correctly, there's a screw under the cap that adjusts pressure on a piece of metal. Pretty technical description, huh?

http://67-72chevytrucks.com/vboard/s...d.php?t=558016


EDIT: OK, I just looked at 3 voltage regulators from my stash. One was an electronic (obviously not original) replacement part. The other 2, both from 67-72 trucks, one my original, were different inside. One appeared adjustable, the other not so obvious. There's also a pretty high likelihood that yours may have been replaced over the years.

Re: Alternator or regulator over charging
 

Thanks! I made a bookmark for it so I can give it to people straight off rather than hinting about it. :lol: