I have replaced the topside control with a new one, but still the heater is not controlled by it. Only the thermostat knob on the AP 1400 will control the heat, and it is not reliable (over heats to high heat shutoff level, has too wide a range in temperature sensitivity between shutting off and turning on heater).

Is there another part inside the AP1400 that might could be the culprit that is preventing the topside controller from controlling the heat like it used to? If so what part is it and where could I locate one? Else, is my only choice to replace the entire AP 1400 control box?

Thanks in advance,

--bill