My system has gone bananas. I have a Potterton Kingfisher 2 boiler, which fires up for about a minute, with higher than normal flue gas teperatures. The pump does not run unless I push the motorised valve (2 port) round with a screwdriver to operate the microswitch. Can anyone tell me where to start checking for the fault? When the pump is running it makes a sound like the water is cavitating within if that gives any clues.
Thanks