Cause of the fault may be:WFXservice manual download site

(1) low-voltage power supply circuit, the regulator ZD2 leakage; R2 resistance becomes larger; Q2 breakdown or open, resulting in +15 V output voltage is low or ov output voltage, the relay does not pull, so that the furnace lights, motors , high voltage transformer 220V power can not be turned on.WFXservice manual download site

(2) low-voltage power circuit rectifier diode D6 resistance becomes larger; filter capacitor C9 failure or leakage, resulting adjustment tube 02 C extremely low voltage, normally can not pull the relay will replace D6 or C7 to troubleshoot.WFXservice manual download site

Three working conditions of the circuit (3) CPU's damaged components should be replaced.WFXservice manual download site