I must be doing something wrong...

My herpstat isn't exactly doing its job - I'm getting huge temperature fluctuations. I have it *set* to 91 degrees, but I'm getting temp readings anywhere from 88-97 degrees.

The temp probe is taped directly to the UTH (and plugged into Herpstat). UTH is plugged into the Herpstat, Herpstat is plugged into wall.

Am I doing something wrong? Did I miss some sort of important step? I read the instructions, but they were pretty vague, so I may have screwed up somewhere along the way.

Arrrgh this is frustrating...