Heatmat buzzes

My heatmat buzzes slightly all the time anyway, I guess coz it's on a thermostat, but when I pick it up to move it I can hear the frequency of the buzzing changing (no - I'm not going mad! :P)

Is this normal or is there a problem with it and I need to replace it?

Which manufacturer is it? I would call them and see what they say. It could be a high resistant connection inside the pad. This could be a dangerous situation. I've never heard of this before and if you think about it, this devise is nothing more than a resistor circuit. Supply 120vac to a known resistance, which in turn creates heat. There should be no reason for the pad to buzz. If it's on a thermostat, maybe turn the thermostat down and see if the frequency of the buzz decreases too. My bet is it will. One of two things has happened, either you have a high resistant connection or the resistor(s) are going bad. To qualify my post, I am an electronic technician by trade.


Good Luck!
Jim Smith