[Jack21]

Simon,

I used a Delco alternator to avoid this, so I'm not really qualified to answer this. There's a post a coupla notches above this one with Ford voltage regulator issues addressed. Check upstairs. Any idea what year vintage the motor, and presumably the alternator is? On the block, just above the starter will be the block letters; something like C6AE-. The first letter is the decade, C=1960 - 1969. Second number is the year. So C6 would be a 1966 year of manufacture. I have some vintage Motors service manuals I use for oldies.

Whatever you do, don't use Lucas. He's known as the Prince of Darkness over here.