Fluctuating water temperature

We've been having problems with our Pulsacoil 2000 for about 6 months now.

We first noticed that the boiler wasn't working properly when the water temperature started fluctuating dramatically when used for longer periods, for example when showering. We tried all the trouble shooting methods on the website - such as ensuring that the header tank was full - but can't seem to find the solution.

We have replaced on peak immersion heater switch as this was proved faulty, although this obvioulsy wasn't the root of the problem.
We have also replaced one of the thermistor rods (the top one). When this didn't improve the problem, we resorted to getting a local plumber to come round and give us his opinion!

He advised that the circuit board wasn't working properly - in that it wasn't telling the pump to kick in when the hot water taps were turned on. He re-wired the circuit board as a temporary measure, so that if we needed hot water we just switched the unit on at the wall. This seemed to solve the problem, though it was a bit annoying having to remember to flick a switch everytime we needed hot water. We have since purchased a new circuit board, fitted it and put the wiring back to how it was.

We can now hear the pump kicking in when the hot water taps are switched on, but the fluctuation in the temperature is back! On looking at the heat exchanger when the water is running, it appears that it doesn't always heat up.

We're trying to find a plumber local to Mid Sussex who can help us out, but the Pulsacoil seems to be a bit of a mystery. Can you recommend anyone or tell us where we're going wrong?

We're fed up with cold showers and having to boil the kettle 10 times to have a bath!

Many thanks,
J&C

hi next step is to change both temperture sensors, this should sort the problem

I agree with Mike, it most likely will be the sensors causing the problem. I would also recommend you have the pump inspected, it may be sticking at certain voltages.