I replaced some capacitors on the main pcb of my Ariston Microgenus 28 MFFI boiler, it has worked for over 6 months without failure. I previously re-routed the flame monitor cable but the fault returned after a few weeks.
The capacitors I replaced were:
C900 10nF 400v polyester (Rapid 10-1860)
C901 47uF 35v Electrolytic (Rapid 11-3814)
C903 0.1uF 275v X2 type ac (Rapid 10-2675)
C904 10nF 400v polyester (Rapid 10-1860)
C905 0.22uF 400v polyester (Rapid 10-1865)
C906 100uF electrolytic 35v (Rapid 11-3816)
Cost of the capacitors was less than £3.00. (from www.rapidonline.com) One capacitor I bought had the wrong lead spacing but I managed to solder it in place.
Donald McNaught
June 2012