Yep, if you're using an older heat pad, it may just be time to break down and buy a new one. I will definitely recommend using a human heat pad with Sterilite housing, though, as I can tell you the reptile pads can warp the plastic, which is a pain even if you have the substrate thick enough that it's not too hot for the snake.

By the way, Smynx, nice to see you back! Looks like you've been keeping busy.