Heater not working properly

[Nathylad]

A slightly strange one. Two days ago, the heater control (the knob that goes from 1 - 4) started to only work on settings 3 & 4. It does not work at all on 1 & 2. Any suggestions or should I just dive in and get behind the controls?

 

[exec]

could be the resistors are shot.

 

[Nathylad]

Is that an easy DIY job by any chance?