i have saunier duval f23e boiler. i have recently changed the reversing valve. it was working fine until few days back it makes whistling noise for few seconds when i put the heating on but when the hot water is used then there is no noise.
Baldev
I had the same problem on ferroli he26c which is less than a year old.
I changed the ignition cable and reset the clock( over riding the programme). The boiler started working now.
Baldev
