If its a combi like ours, we had the same problem easily solved-I take it it fires for about 20/30 secs then cuts off. If so then check for any dripping hot taps and turn them off-this confuses the diverter valve and stops the flow. if this fails then it probably is the diverter valve.
Steve walton
December 2010
Simple things to check first:
Timeswitch on, room thermostat turned up?
Carefree
December 2010
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