As noted above, the cabin air needs to be cool as the seat fan just circulates the air that's available inside the cabin. Making sure the A/C directs some of the air to the floor/foot well area will ensure there is cool air to circulate.
I've used this feature in my Stingray several times and it works. I've had to reduce the fan speed to the lowest of the 3 settings because the air was too cold.
