Saunier Duval F30e combi boiler: HW is okay on its own, CH is okay. But when CH is on and HW is turned on, the boiler tries for a few seconds and then shuts down with F9 in display and red light flashing. Pressure is bet 1-1.2bar. Have replaced water pressure sensor; gas valve stepper motor and 3way valve head piston(pin) working okay. Any help out there will be highly appreciated. Thanks.
Thank you, but I suspect something mechanical, and am going to remove and inspect the 3way valve as soon as weather permits (the boiler is located in an outside toilet!). Will let u know when I find something.
The Manual states that F9 indicates:
1. Water pressure sensor - but I have changed that with no results.
2. Stepper motor - I have checked this according to their instructions, and it works. I also checked the motorised 3way valve head, and it works.
3. Overheat stat (manual reset) - but the stat does not trip!
That is all the help they can give, hence my cry for help.
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