My Baxi Solo 3 50 PF is about 8 years old, we have had a new circuit card put in about 18 months ago and have had no other probs up to now. The problem now is that the boiler turns on for about 50 seconds and then turns itself off. Repeats this cycle every 7-10 mins. The water is luke warm but the radiators have got no chance. It started this yesterday evening. Occasionally there is a banging noise coming from the top part of the boiler when lighting as if it can't fire up, it does eventually lite, but only for 50 seconds! Any ideas please.