Potterton Boiler / Switchmaster 400 - problem

12 Nov 2006
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United Kingdom

Ignorance doesn't really adequately describe me in relation to boilers and central heating so if i don't provide the relevant info please let me know and I'll do my best to get it.

I have a relatively old Potterton Kingfisher boiler with a Switchmaster 400 timer system on it. The timer unit has a 24 hr clock with brown and orange pins to set the on/off points and two rocker switches to the right of the clock which allow for Timed / Off / Constant and Water / Water and Heating options to be selected.

Underneath that unit is a blue box with Switchmaster on it and a white dial in the centre - this is what I suspect may have the problem btw - there are 4 options set around the dial, at the top is Turn, to the right is Central Heating, to the bottom is Central Heating and Hot Water and to the left is Hot Water.

Now up until yesterday the dial in the centre of that blue unit would turn automatically (albeit very slowly) to the relevant setting as determined by the timer or by me over-riding the timer by clicking it onto Constant. Now, although the pilot is on and the boiler is fine it will not move of it's own accord. There is a slot in the centre of the dial which a 2p coin fits nicely into and I have to twist the dial manually - at which point the boiler will come to life and heat etc is provided.

I have it on constant at present (because it's outside the timer hours) and it's fine once it's started but if I then lower the thermostat (on the wall) until it clicks off, increasing the thermostat again will not start the boiler up and I have to manually move the dial on the Blue unit again.

So, apologies for the lack of proper info and the length of the post - any thoughts from the sages out there?

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Just junk the old controller and fit a new one. Their not that expensive.
you cannae get them any more

but a honeywell three port will do you just have to change the pipework AND the wiring

my advice is get someone competent in
I agree with Corgiman, you have a Randall HSA or Switchmaster valve and its knackered.

You need to replace it with a new 3 port but you will need to rewire the system.

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Thanks for the replies - it's appreciated - sounds expensive though unfortunately. Perfect timing as I'm due to move out in two weeks and I've signed up saying the heating's fine.... :evil:

Any chance of a rough estimate of costs for this and can anyone recommend 'someone competent' around the Farnham (Surrey / Hampshire border) area?

Thanks again.

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