Quoted from wayout440:

IMHO, why add a fan at all? Fix the problem, a fan is a patch. These games are designed to run for years without them, and many exceed those expectations with the type of care we give them. Flipper coils should never get hot. They should survive plenty well even if they should get warm....but this is usually the sign of a lurking issue. Fans themselves draw in extra dirt and dust, they add noise, add current draw, and they'll need attention sooner or later. Even when I add supplemental power supplies, I avoid fans and go for open frame fanless supplies. The only game I know of that requires a fan is Pin2K, because the design uses an off the shelf computer system.