Help - only get CH when hot water is on - broken valve?

4 Nov 2003
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United Kingdom
Hi there,

I have a Potterton Flamingo 40 boiler in an open CH system (Honeywell programmer, Grundfos Selectric pump, ACL 3 port valve, Drayton mechanical room stat).

Whenever I turn on the hot water it works fine, and the same goes for the CH if the water is on. But the CH will not fire up in the boiler if I just turn on the CH - although the light on the controller does come on. The switch in the valve does not move when the CH is turned on.

Could it be the valve motor is kaput - or more likely that the room stat is not working (temp is turned right the way up to try & make it fire)?

Help v.much appreciated!
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doubt full its the room stat mate

must be the three port valve motor have you pushed the arm over on it to manual?
Thanks for the advice - um, how do I do that? There seem to be 3 potential positions for the arm. Currently it's on the left hand side - but there a wider space to the right so it can go right upper or right lower?

And having done this, how do I test it?

Thanks for your help corgiman...
when you turn the heat on can you feel the arm move


if you dont defo the motor
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It doesn't move an inch when I turn the CH on.

Are motors easy to replace? It's an ACL Drayton 3 port valve ...

I dont think you can change the motor on a ACL valve

but a new head should not cost more than 40 plus vat from a merchant and you just change it like for like easy peasy lemon squeezy

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