There are 6 heating elements located inside the SH1500. 1 Long and 5 Short. The Long Element is located up by the vent where the heat comes out. Not all elements will go out at the same time. It is best to open the heater up and inspect the element to know which ones will need to be replaced. Remove the right side panel (opposite the power switch). Plug the unit in, and see which elements are not glowing red. “Dead spots” or blackened elements will be a sign they are about to go out. For element location, please refer to the wiring diagram in the repair guide.