You need to trace the electrical connection into the units junction box on the unit,then from there locate the units thermostat and bypass it to see if this lets the element heat up just to test it dont leave it this way and walk off as it will overheat if the element heats,if it doesn't heat,then you know its the element itself,and a simple continuity test will confirm this problem,theres not much else that can go wrong.

There could be a couple problems to check -- check to make sure the temp sensor is set to the desired temp and make sure it is operating properly. also - the heating element could be starting to fail and needs to be replaced.

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