My first comment is the probe placement. They must not be able to move and the snake should not be able to get in between the probe and the heat source.


I am also looking for some clarification, one probe is not reading 90º and is not shutting down at all? The other is reading 90º and is shutting down correctly? Are the temp reading coming from the herpstat or other thermometers? Most digital thermometers have an error range the vast majority are 2ºF from correct some (very popular ones) are specd at 4ºF from correct. If you are using a digital thermometer to read the temps it is likely they are not going to read the same. I would suggest using the same one and see what they come up with. Or use one of the empty probes of the herpstat to check the temp.