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My alpha 240E fires up and cuts off on both hot water mode and hot water and heating. It runs for approx 30 secs to 1 minute then cuts out. I have tried hot water mode only and it heats up the water. It does not go through to the heating pipes. I have taken apart both primary and domestic hot water valves and both diaphragms are both in good condition. I have cleaned and greased as many moving parts on the divert valve. The fan and venturi have been cleaned. Has anybody got any suggestions. It just keeps firing up and shutting down.