Central heating switching it's self on.

[supermoto]

Hi,
I'm having a problem with my central heating. The radiators are intermitantly getting very hot and are not being regulated by the room thermostat (e.g. the central heating on the timer control unit is off).
I believe It is a fully pumped system:
Netaheat Profile 40e gas boiler
with a Honeywell 4073 3 way valve.
The problem seems to have started since returning from a few days away when the CH and HW controls were switched off
Am I correct in my assumption that these problems are caused by a faulty 3 way valve?
I ask as the valve head has been making strange noises and the problem seemed to have been cured the first couple of times by a sharp tap with a screwdriver handle.
Now having taken the cover off it seems that the motor is starting to stretch the spring but then letting it lose a bit of tensen while making "psst psst psst" noises as if its supposed to latch into a position with the spring under tensen but is not quite making it.
Is this the problem or am i just going off on a tangent???

Thanks for your help

Matt

 

[ChrisR]

No, you got it, you need a new head. Could do with one myself these days.

Assuming you have a pimple on the head's lid, undo two screws to remove the head (=actuator) from the body of the valve. Make sure the spindle moves freely, over about 30º; they can stick.

With the head off, the mechanism is very sloppy. so you can't judge it then.

 

[supermoto]

Thanks for the speedy reply!!

Assuming you have a pimple on the head's lid, undo two screws to remove the head (=actuator) from the body of the valve.

Yes the lid has a pimple on the the top ( just behind the lid fixing screw.)

So a replacment head will solve my problems will it??
I assume you can replace this without getting wet

Make sure the spindle moves freely, over about 30º; they can stick.

If i find this is sticking how would i remedy this??

Thanks
Matt

 

[ChrisR]

Yes you stay dry to change just the head.
If the shaft is stuck you can wiggle it hard with a baby spanner, with a little wd40 or silicone spray if you need it.

If it's leaking or really stuck you have to go deeper, with the whole or wiggly parts of, a new body.