microgenus 23 hot water fault

[puzzymunkle]

I have a microgenus 23 that works perfect on heating but when using the hot the temperature fluctuates. It gets very hot, cuts out goes almost cold and then fires up again to repeat the same process over and over. I recently replaced the diverter valve for another problem so its not that. Could it be the probes? Also, when it fires sometimes it buzzes momentarily. I dont think the 2 are linked though. Any thoughts would be appreciated to get this done as cheap as poss as it is going to be replaced this year when I do a loft conversion. Any thoughts on the worcester bosch combi? Thanks in advance. Steve
Just checked my receipts etc and I changed the dhw and ch temp probes with the diverter so prob not that either! Could it be safety cut out or would that send the boiler into shut down and need resetting?

 

[frankthegasman]

the problem is that the domestic hot water heat exchanger has muck in it you will have to get it exchanged and possibly get the system flushed as the muck comes from the central heating circuit if you install a new boiler later this year you will need to get the system flushed for this anyway good luck

 

[weareleeds]

Likely cause is incorrect gas valve pressures or thermisters out of range

 

[puzzymunkle]

Any idea how much the dhw heat exchanger costs please? Is it possible or viable to get non original parts? Steve

 

[puzzymunkle]

Likely cause is incorrect gas valve pressures or thermisters out of range

Why would the gas valve pressures change? and what are thermisters? Steve

 

[frankthegasman]

you can get this at most agents about 50 quid its held in place by 2 allen key headed bolts and you will need an allen key with a ball end to get the one out from behind the pump its a bit fiddly and water runs down the wall as you remove it if in doubt get a qualified gasman to ex it ,good luck