can anyone give me some advice on my 24i rsf combi, the problem is when i turn the central heating on it blows the reset button after about 20 seconds, the hot water is fine, and i`ve thrown lots of cash at it by replacing the fan, as this wasn`t working, pcb, as the troubleshooting guide advised this, over heat switch and thermistors, just because i felt like throwing 30 quid at my boiler, and still no central heating, i switch it on, it ignites, then as the water is about to be pumped through the reset button pops, help please.......