My Potterton Puma 80 boiler is showing low pressure warning. Ive looked at numerous other posts to check problem. The pressure is in fact way over in the red (4 bar), ive bled radiator to get it down to +- 1 1/4( black gauge now sits on red gauge). Ive also followed 2 yellow wires from PL12 on modulation control board to behind the board( by removing retaining screw and pulling board down) to what i believe to be the CH water pressure switch as noted on boiler wiring diagram, however ive noted that the diagram for CH water pressure switch is square with 1 & 2 connectors for yellow wires where the "switch" at back of board is round with 3 x connectors( 1 insulated) with 2 yellow wires going in. In a previous post it is recommended to disconnect these wires to override safety feature that stops boiler firing and let it run for a minute, then reconnect which apparently fixes problem by resetting it, this in my case did not work. Another post suggest putting 1 of the yellow wires into the 3rd unused connector, running system then returning wire to original position, again this didnt work? Lastly a suggestion is made of cleaning a blockage out of the switch( and excuse my lack of knowledge but we are presumably not talking about a conventional sort of switch as it has no"switch" mechanism that i can see...is it internal?), however there is no explanation as to how to remove and clean the "switch". If at all possible i would like to fix this myself/clean the switch as i already had the boiler looked at 4 months ago as the timer wasnt working and that cost me a whopping £400 by the time it was resolved. Please help.