One thing you could do is put both the UTH and the bulb on the same side for a while and see how hot it gets. Don't do that while the snake is in there, or else stand there and watch the temp gauge, because it might get way too hot. But at least it would be a start to proving there isn't something messed up with the temp gauge.

If the room is really cold or drafty, you may just need more heat.

I would also suggest you start a new thread, because this really has nothing to do with the title anymore, and you might also get more responses that way. In your first post, put all the details about your tank size, what equipment you have, etc. etc.