When the water is running the temperature if the water fluctuates between burning to lukewarm to cold and back to hot!
Could this be a problem with sludge in the heat exchanger?
Maybe it would be a good idea to clean this out (eh X400) prior to fiddling with the thermistors?
I have a Worcester Bosch 28 Combi boiler which was fitted new 6 years ago.
Over the last few weeks I have been getting initially hot, but then lukewarm and cold water from the taps & shower. The heating system is working fine.
I'm not entirely sure where the problem is but I feel it may be...