Before you do that--->Disconnect power to your wall oven, then ohm test the high limit switch(thermostat) for continuity, if that is bad you will get no heat at all in the upper oven.
Use your multimeter to ohm test it for continuity. Its behind the back access panel on the back of your oven. You will need to pull the oven out from the wall to get access to it. I'd suggest having someone help you pull it out from the wall, these wall ovens are heavy.