I have a corn snake, and got a proportional thermostat cheap from a friend. Where do i put a probe on the hot side of the tank? I have a thermostat, and a heat pad with a heat lamp to keep it warm (room is pretty cold, not heated), the heat mat is on all the time and doesnt make a difference at all if i turn it off completely, come back a couple hours later and check the temp its still exact same. Thing is the temp fluctuates alot (over 10 degrees F) just leaving it all at the same heat. One day it'll be 76 F next time i check its like 86 F.

I would think to put the probe on the hottest spot that the snake can go (right below the light, highest point possible) and get a bigger heat mat to use with thermostat, but apparently heat mats dont heat the air inside of the box. So i got a ceramic heater thinking it would work with the thermostat to keep the temps good, but the temperature just goes all over the place (fluctuates over 10 degrees F) in the hottest spot, even with a proportional thermostat.

When you want to control the heat on the hot side of a tank, do you place the probe on the floor of the tank, or at the hottest spot?

Also to use the thermostat i have what should i get for a heat source? a bigger heat pad?

Any help really appreciated.