could any one tell me what is wrong with my Baxi combi 80 boiler.When i turn on the hot water tap the boiler will try and start up,the fan will start and stop and this will go on for some time.the boiler burner will take 2 to 3 minutes to light so you will have the water running for about 3 to 4 minutes before i get any hot water though.Also the water is not that hot some of the time.If any one could help that would be great.Thank You all.