3 way valve changing

[stubanks]

I have a open vented system where my rads are heating up when only the hot water is on. My 3 way valve is either stuck or not working although it once was. It is not electrical as I can see the spring trying to move. My question is do I drain down the whole system from the bottom most rad and will that allow me to crack the pipes and inspect/change the valve? Do I also have to drain my hot water tank or will draining from the bottom rad be enough. I have heard that these can stick but I cant see away of taking off the solonoid without removing the whole unit.

Thanks for any help.
Stu

[Reynoldspc]

What make of valve is it?

[stubanks]

Its a Honeywell V4037A 22mm

[Reynoldspc]

Hi, turn off the supply to your feed/expansion tank and drain from the bottom rad, you don't need to drain your hot water cylinder. with the electricity off you can remove the metal cover to the valve. inside you will see four screws which hold the motor and switches to the body, remove the head, you will see that there is a wee ball which controls the water flow through the valve, it is probably worn. You can get a Honeywell service kit for these valves from HRPC, part of the plumbcenter group, consisting of a replacement ball, clip and "o" ring, it's cheaper than replacing the entire valve. You replace the bits in the kit, put it back together and refill the system. Job done :)

[stubanks]

Thanks for that. I had already bought the unit off ebay for £30 which wasnt a bad price and have changed it and its working great now, I will remember the tip about a service kit should it happen again.

Stu