Potterton Suprima 60 Fan runs and the ignition sparks however as soon as the burner lights it trips the main fuseboard RCD. Spoke to Potterton Tech they told me to test between the red and black cables on the gas valve it should be 4.6K ohms it only reads 3.5K onms. He suggests changing the gas valve (not sure) any thoughts

phil, October 2010

sounds like it may be the gas valve if it's blowing during ignition, but 3.6k ohms should not cause it to blow the fuse. disconnect the lead from the gas valve and turn the boiler on, the gas valve is the last thing in the ignition sequence (except flame rec which is low voltage). it won't light, but if it doesn't blow the fuse then i'd bet the gas valve is at fault.

Ian, October 2010