Biasi m90e 24s Combi intermittent Very hot water then Cold, then very hot, then cold.

[Neddy1984]

Hi,
a friends Biasi m90e 24s combi was working fine until recently. now when she has a shower the water goes from very hot to very cold, and back again every 20seconds or so. Could this be a partially blocked or scaled up heat exchanger that needs cleaning out? any suggestions would be very welcome. Thanks in advance

 

[moogwai]

I would say that.....check the diverter ain't letting by and dumping down the ch flow pipe.

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