Whats the temp right above the heat pad. And 83 on cool side is still fine dont worry about that.
If you have your heat pad plugged directly into a wall outlet and thats it, i can guarantee your hot side is over 100 on the glass. You need to get a digital thermometer that has a probe on wire so you can have it on the warm side to read the surface temp above the Heating pad.
Also want to look into getting a lamp dimmer or thermostat to control the temps so you never have to worry about them