You need to have some one check the continuity of the thermal fuses at the plug where it plugs into the side of the control box. It's a two pin plastic white plug with black fabric covered wires coming out of the plug, you should have about (0) resistance or maybe 1 ohm. If you have no reading at all you will have to pull the heating coils out. Not a big job but, the unit must be removed from the wall as you have to take off the long top metal plate. Remember you do this only if you have to get to the coils. You can get the the plastic plug with out removing the unit but unplugging the plastic plug this may be a little tough but, you can do it.
Make sure you pull the Power plug out of the unit or out of the wall before testing for continuity.
I hope this helps. I put a picture below. It's the only one I have. On the right of the unit under the control panel there is a metal box you can see the front if it in the picture. Most units have this box on the right side. On the left side of the box are the plugs for heat, fan and Thermal fuses.
There maybe another plug with yellow wires. the plug with the 2 black wires is the one you want. Squeeze the side of the plug to unlock the plug then just pull out and test.