The digital display window shows 150 degrees F, but the firing chamber is glowing red. What is causing this?
Disconnect the power, open the control panel (switch box), and check the thermocouple wires, especially at the back of the controller circuit board. (The thermocouple is the rod that extends into the firing chamber. It senses the temperature.) You will find two wires that run from the controller to the thermocouple. Color coding for thermocouple wires:
Type-K thermocouple: yellow wire (+ terminal) and red wire (- terminal) with brown or yellow outer wire insulation
Type-S & R thermocouples: black wire (+ terminal) and red wire (- terminal) with green outer wire insulation
Look for bare areas of the wire where the insulation has been stripped too far. The first place to check is the wire ends that attach to the back of the controller. If the bare ends cross over and touch, the thermocouple will register the temperature of the switch box instead of the firing chamber.
This problem takes only a moment to fix. Remove the wires, cut them a little shorter, and reattach the wires to the controller.