an ac is more effective for chameleons, if you have and galsenlcosure you can freeze a (cople) bottle of water and put it in his cage at nioght it helps llower the temp a bit
The issue with using a fan is that it will dry the cage out faster, and if the air in the room isn't cooler, it will just circulate the warmer air. Any cooling would be from evaporation of water droplets in the cage. You will need to watch the humidity level so it doesn't drop too low for your jax.