We have a Worcester 24i boiler (about 8 years old) The PRV was broken and not holding any pressure so we replaced this and as a consequece found a leak where the flow switch is housed. When we went to tighten this the whole thing smashed. We got a new one, put it in, we try turning hot water on and off about 10 times and it is fine. Leave it for a few hours then the flow switch will not turn itself off after you close the tap and hence the boiler overheats and shuts down. Can anyone help. Do you think it's a faulty switch or have we put it in upside down (doubt this because it initially works)?