When the heater unit encounters conditions outside the parameters for safe operation, the logic circuits on the main circuit board may throw a fault code. This self-diagnostic feature helps protect the user and the heater unit itself and also points the user in the right direction for diagnosing the issue. The procedure for resetting a fault code is simple with the Propex heater but requires attention to the timing of the reset operation.
To reset your Propex heater, turn the thermostat temperature knob to full hot and then turn the operation dial from OFF to FAN to FLAME then to FAN to OFF then again from OFF to FAN to FLAME. The speed at which you turn the dial is extremely important, just under a second each direction. Please see the video at this link for an illustration of the timing of the procedure:
If you have a digital thermostat, please take a look at the video below.