What happens when you apply the clockwork construct template to a golem? The template gives electricity vulnerability, but golems tend to be immune to almost all magic.
Vulnerable to Electricity: Clockwork constructs take 150% as much damage as is normal from electricity attacks
Immunity to Magic (Ex)
An iron golem is immune to spells or spell-like abilities that allow spell resistance. Certain spells and effects function differently against it, as noted below.
A magical attack that deals electricity damage slows an iron golem (as the slow spell) for 3 rounds, with no saving throw.
A magical attack that deals fire damage breaks any slow effect on the golem and heals 1 point of damage for each 3 points of damage the attack would otherwise deal. If the amount of healing would cause the golem to exceed its full normal hit points, it gains any excess as temporary hit points. An iron golem gets no saving throw against fire effects.
An iron golem is affected normally by rust attacks, such as those of a rust monster or a rusting grasp spell.
So what happens?
1) The golem remains immune to the spell lightning bolt but should be careful in a natural thunderstorm taking x1.5dmg.2) The golem is no longer immune to magical lightning and will take x1.5 dmg from any electricity.
3) The golem retains its immunities but any special effects (such as the duration of an iron golem being slowed) are x1.5
Number 1.
base damage x 1.5 (vulnerability) x 0 (immunity) = 0
(Though Number 3 would be a very reasonable house-rule, as long as you informed your players of course.)