SH18 SH25 WF25 - FC7 service diagnostic fault finding
FC7 - Ignition failure after 3 x ignition attempts
If heaters burners ignite but spark continues for approximately 7 seconds and then burners extinguish the flame is not being sensed
– Therefore, most important is to check signal strength.
If flame sense signal is low investigate the electrode and and flame sense leads
- Check signal strength with a multi meter set to DC voltage
- Start heater and when flame cross ignites and is present at the flame sense electrode, measure DC voltage across metal terminals FC- and FC+ on the EFS (Fenwal).
A reading of 1.5 to 2 Volt DC is considered good signal strength. Any values below 1 Volt DC need to be investigated and rectified.
FC7 after the burners ignite but extinguish after 2 to 3 seconds can be caused by recirculation of combustion products into combustion air inlet
Check the flue has been installed correctly paying particular attention to the flue terminal fitment - see below for guidance on flue terminal fitment
