HALSTEAD FINEST GOLD SHOWER ALTERNATES BETWEEN HOT AND COLD?

[coops1]

Hi,
I am hoping you can help me. My shower flutuates briefly between hot and cold for no apparent reason. It is a no frills shower with just an handle that you swivel side to side for temperature, and up and down for rate of flow. It is powered by the Halstead Finest Gold combi boiler.
Any ideas? Please!
Regards,
Coops.

 

[ChrisR]

Run a hot tap at a LOW rate, about 4 litres/minute.
If that goes hot/cold too, it's probably sludge in the boiler, probably cleanable - until it does it again.

Sludge usually causes hot/cold periods of half a minute or so - if much quicker then would suspect the shower mixer.

 

[coops1]

Hi,
Thanks for your quick response.
The sink mixer tap fluturates a little but not as much as the shower.
The mixer shower is alternatively hot for approx 30 seconds and then goes cold for approx 7 seconds.
Does that help the diagnostics?
Regards,
Coops.