Halstead Platinum Water Pressure Switch

[f1larry]

Does anyone know what this switch looks like?
Basically my bro's boiler's does a system check when its switched on and throws up a 'water pressure switch inoperative' fault.
According to the manual I should:
- check the water pressure is above 0.5 Bar - which it is.
- check C/H pump - I'll take the silver centre cap off and check the pump spins up when the boiler's switched on (not done that yet)
- check expansion vessel - I'll check the pressure is above 1 Bar and that no water comes out from the valve when depressed (not done that yet but will follow guide on here)
- check switch. Is this the microswitch that is activated by the C/H flow valve?
I wondered if the valve diaphragm could have a hole in it? The actuating pin from the valve makes no attempt to move when the boiler's switched on but also offers no resistance when moved with a small pair of pliers, leading me to believe the diaphragm may actually be ok.
I'm probably going to go over tomorrow for another look at the boiler - have I missed anything or does anyone know of any common faults with these boilers?
Cheers,
Larry.

 

[f1larry]

Just in case anyone comes across this thread; it turned out to be the pump capacitor in the end. I purchased a replacement motor capacitor from Maplin for £3.50p and we're up & running again (for the time being!). I was a little annoyed with myself as the pump was the last thing I looked at as I was told they rarely fail. Furthered my knowledge about combi boilers in the process though! Tested motor by removing it from boiler and and connecting it to a wall socket with a plug. The motor wouldn't turn without a little help from my foot - replaced capacitor & it started up straight away.
Many thanks to those who contributed to the FAQ and boiler wiki - most helpful.
Cheers.