Just fitted a new alternator to my 69 F100 - 1G 65A version, which is about as high output as I could find for a 1G and I think is higher output than the one it replaced.

Started the truck up and it ran fine, but I also noticed that one of my headlights had blown - coincidence??

checked the voltage across the battery and it reads 15v with the engine running. Seems too high - think 13 to 14.5v is where it should be at. Could this be the voltage regulator? I actually fitted a new voltage regulator a couple of years back but I'm thinking maybe it's rated for a lower output alternator. I can see the AC Delco F609 is rated for use with alternators up to 100A so that could be the correct one for me.

 

I have never heard of voltage regulators specific to alternator output in cars and pickups. 60's through 80's before integral voltage regulators Ford only had 2 regulators. The original points style which was replaced by the electronic one. This went on cars and pickups 38 amp through the big case 100 amp. Maybe you have an aftermarket regulator that can't handle it?

 

Voltage regulator regulates voltage.( I know master of the obvious) If you battery is low it could put more voltage to the battery. 15V could potentially boil the fluid in the battery. Sounds like you should change the voltage regulator to me. Why didn't you opt for the gen 3 alternator? Easy to find, more powerful and internal regulator.

 

i thought about it but I'm in the UK so possibly not as easy to find as in the US. Though I'd guess that the same alternators were used on some UK market Fords, just not sure which ones. It's something I'll do at some stage though.

I ordered a new voltage regulator.

 

You should check out HIO Silvers Read first Read First: Technical Info Hyperlink Compilation ( 1 2). Lots of good information there. I'm sure 3G ford alternators come in all sorts of cars and trucks. If you gave HIO Silver a shout out he likely has a list of known donor vehicles many would be available anywhere. Good luck. Keep us posted.

 

Make sure the regulator "sees" a solid ground, if it's lifted relative to ground they lose their reference and can peg to the high side.