Hi
Ive got the same problem as you my hot water keeps going hot and cold about every 20 seconds, The sensor you are on about is called a "domestic hot water water flow temperature sensor" it is easy to change as i have done it. the sensor's come in a pack of 2 from plumbcenter at a cost of £ 20. However this has not sorted the problem out. As Ive been going through the trouble shooting guide in the book i now believe that the problem is the gas valve its self whitch im trying to get the best price for at the moment whitch is about £130 ish.
paul fleming, January 2008
