I had this problem with a baxi boiler. Suggest you check the flue. If the boiler does not vent properly then the gas builds up in the top of the exchanger and kills the flame. The flue may be blocked so check the point on the outside (birds nests, twigs, leaves etc). If this is clear then watch the flame ignite inside the boiler through the inspection and see if it fades before going out (takes about 10 seconds). The chamber is fed through an extractor fan at the top of the boiler. This may be faulty also, which starves the boiler of oxygen. It could be the guys that put the new exchanger in did not seal the exchanger to the flue properly. Could be dangerous to your health suggest you get a carbon monoxide tester (about £5) and put near the boiler just to be on the safe side.
Robert, February 2007
