I went to this one a couple of weeks ago and as there was a noise like noisy bearings coming from the fan area of this boiler i got a new fan for it. Went to fit it today and it hasn't cured the problem. This boiler is fine on DHW but on CH it fires up and after about 10 secs or so it goes to a low flame and then either picks up or gets so low that it goes out. After about a minute it fires back up and does the same again. I thought (with the noise it was making) that the fan was on its way out but i was wrong. Has anyone any other ideas. Pump is a little noisy and when i took the central screw out black water came out. Pump is working. Now i'm thinking that maybe the CH flow filter may be blocked? Tennant has had everything changed on this monster apparently. PCB a couple of times. From reading some of the posts it seems Gloworm have had problems with PCBs on microns? Originally the bloke at the house had put a cowl over the end of the flue so i took that off but it didn't make a lot of difference. Also it is in a ground floor flat and it feeds rads for 3 floors above also. I'm guessing that all the tennants must share the bill. Any ideas anyone?