firtly the water pressure is too high (should be 1-1.5 bar when cold) bleed excess from a radiator (do not use the safety valve!)
you said you checked the micro-switches, and say they make, assume you also checked the switch with a mutlimeter to ensure they are working too, and checked the voltages reach the pcb terminals...
would be suspecting a pcb fault if all checks out
T
July 2008
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