yeah, got correct voltage to gas valve, checked resistance through boiler stat - that too seemed ok. home owner has had a vokera service agent out since who replaced the pcb - apparently the problem hasnt gone away. hot water still too hot even with stat down etc etc.
yeah the problem...
had a gas valve that wouldnt modulate between min and max burner pressures. if i set it to either, it stayed there regardless of demand or number of wires attached.
changed valve - problem stayed same. check wires for continuity etc, everything ok. rang vokera - they said it HAD to be the gas...