If the ambient is pretty much the same then a fan won't do anything.
Iv never heard of someone not having a hot or cold side like suggested above so I don't have any experience with this. I will say that I definitely DO NOT agree with doing that ! A snake needs to thermoregulate and I think it would be cruel not to provide them with that.
Only way around keeping them in the garage and providing the right care that they need would be to cool the garage or at least the area that they are living in
Or if your quite handy you could set up some sort of liquid cooling to create a cool spot which would be pretty sweet. Never seen anything like that before.