SHOWER GOES HOT AND COLD

hI

I have a wee problem . The pump on the boilermate 2000 is going on and off , with in turns fires up the boiler on and off. This doesn't happen all the time .

Also in the shower the water goes from hot to cold then back to hot .

Any ideas is it a boler problem or a bolermate 2000 problem . The boiler is an ideal boiler.

Changed the room thermostate thinking that may be a problem but no change. Have changed all the sensors apart from store sensor.Could the heat exchanger be blocked?

apart from the shower do the other hot taps /bath /handbasin /kitchen all work ok ?
if yes than the shower thermostat is your problem.
mark.
www.gledhill-repair.co.uk

I have exactly the same problem also using an Ideal Classic Boiler. The problem affects all my hotwater taps and shower. Do you know what may be causing the problem. Thanks