i have a potterton promax 28 he combi boiler that won't work the spark genorater, electrodes, gas valve and pcb have all been replaced and still no joy help
each boiler has a start up sequence ie. call for heat/water -pump starts if the pump is proved fan starts -fan operates pressure switch which starts spark generator and so on find out start sequence and go from there don't assume new parts aren't faulty realisically you need a multi-meter and all the technical specs either try potterton tech help line or web site
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