I would have thought if the continuity checks out on the gas valve, the engineer then tested the pcb? This means that the water will take longer to heat but on the flipside, you’ll be saving energy! (and therefore money). The popularity of combi boilers means that a majority of boiler engineers are trained how to repair and service them this makes it easier to find qualified engineers in your area. I called a few plumbers on friday night jim was the only one that answered.