1970 F100 302 2WD SWB AUTO.

On my way home Friday I noticed my volt meter reading between 15 and 16 volts at 2,000 RPM and about 13 at idle (600 RPM). Normally at 2k I would get just below 14 volts and if I had the blower on I would get just 12 volts..

So today I load the bed up with some stuff for my mother-in-laws garage sale, hop in the truck flip the switch turn the key and nothing... Check battery voltage and it is at 0.38 volts (checked three times with two different meters after checking one of the boat batteries). Battery was new in January.. Voltage regulator (thing on front by radiator, battery side) looks original.

Any Ideas what to change besides the battery?

 

jsalty, charge it up if you have a charger, swap in another charged battery if you don't, drive it to your nearest favorite auto parts house and have them provide a free analysis. I suspect alt. but V. reg is suspect too.




John

 

Battery would not take a charge, store tested it said it was bunk. Had the voltage reg tested the results were conflicted. The test said it was half good. So I am replacing it. Will take the truck to the auto parts store once the new bat is installed for a alt check.

 

Yeah, from the symptoms you describe, it sounds like the battery was the victim, and the regulator was the cause. The regulator locked on and told the alternator to "give it everything you've got!" The battery overheated, boiling out enough water that the plates shed electrolyte, and finally shorts out in self defense.

So, yes, replace the regulator before putting in the new battery. If you get 13.0-13.8 volts the alternator is probably fine.

In general, if you see over 14 volts, you're killing the battery. You may be able to drive it home, but the battery will see permanent damage.

 

[QUOTE=xstrange;8972452]Yeah, from the symptoms you describe, it sounds like the battery was the victim, and the regulator was the cause. The regulator locked on and told the alternator to "give it everything you've got!" The battery overheated, boiling out enough water that the plates shed electrolyte, and finally shorts out in self defense.

So, yes, replace the regulator before putting in the new battery. If you get 13.0-13.8 volts the alternator is probably fine.

In general, if you see over 14 volts, you're killing the battery. You may be able to drive it home, but the battery will see permanent damage.[/QUOTE

Thanks for the info. I figured the voltage reg crapped out when I noticed the 14+ volts on the meter.

Will check the alt output to bat when I install battery tomorrow.

 

howdy my 72 4x4 f-250 had similar problems replaced v reg alt an still low voltage so i converted to a one wire chevy style alt that had internal reg . when i started the truck had to rev it to 2000 rpm to excite the new alt but it solved all problems going on 7 years now . plus i was able to eliminate a bunch of wires an the old v reg i can take some pics if you want