Hi all
Tried all of the above and my Worcester Bosch 28i RSF still wasn't fully functional.
When i disconnected the red tube and blew into it i heard the clicking the boiler fired up but then when i reconnected and pinched it numerous times i still got nothing.
I traced the red tube as it changed to steel pipe up the side casing which changed back to the red tube and then which attached to the fan. I pulled the red tube off the fan and blew straight through that red tube, the steel pipe and the bottom section of red tube for blockages and it was all clear.
I then checked the fan itself and it was a little stiff. I loosened it up and got it running a lot easier and then connected everything back up.... Now working like a dream - Success!!!!!!
Jim Smith - Wannabee Gas Engineer!!!
January 2013