wrote:
> Just tried my '66 GTO's mechanical voltage regulator on my friend's
> '69 Firebird and it started charging his battery again. Even though
> he had bought a new voltage regulator a month or so ago. (And then an
> alternator.) His does not have the condenser installed on the voltage
> regulator like mine does, but there's a terminal for it.
>
> I'm wondering if the condenser is necessary, maybe to keep the
> contacts from burning? I'd heard it was to prevent radio
> intereference, which we don't care about.

Both of the above. The regulator is switching an inductive load, which
causes a huge voltage spike (and resulting arc) when you interrupt it by
opening the contacts. The condensor damps out the voltage spike and
prevents the arc. The arc is what causes radio interference.