How stiff should the 3 port valve be?

[fronty]

Had a couple occasions where roomstat was calling for heat but boiler wouldn't fire. Wiggled the head on the 3 port valve (Drayton MA1) and the lever would then move from M to H, there'd be a click, the pump would come on and the boiler would fire. Actually on both occasions it looked like the lever was just past M.

Seems something is a bit sticky. Took the head off and tried turning the valve spindle by hand, it's quite stiff, I have to use a pair of pliers. Was wondering if the motor is getting a little knackered and it's struggling to turn the spindle, so don't know whether to change the head or the whole valve. Should I be able to turn it with my fingers?

Cheers, Fronty

 

[Best]

Yes, you should be able to turn it with your fingers. Compare it to a new one.
Although they generally do get stiffer with age

 

[ShaunCorbs]

Head off

Put some wd40 down on the spindle and work it back and forward should loosen up

 

[fronty]

Head off

Put some wd40 down on the spindle and work it back and forward should loosen up

Just circling back on this, worked a treat, no probs since I did this and can now turn the spindle by hand, thanks for the tip.

 

[Ric2013]

WD40 on rubber O ring seals? Waiting for Dave to tell us it's going to wreck them.

 

[ShaunCorbs]

WD40 on rubber O ring seals? Waiting for Dave to tell us it's going to wreck them.

Don’t think there any oring s

 

[Ric2013]

So what seals the spindle on a 3PV? Is it a graphite seal?

 

[ShaunCorbs]

So what seals the spindle on a 3PV? Is it a graphite seal?

Think it’s a mating surface

 

[fronty]

Well this is just sods law, as soon as I say I fixed it, it plays up this evening. I did a little video so you can see what's happening...

 

[SJB060685]

Before posting this video did you check to see if valve was stiff again Before doing your wriggle trick?

 

[fronty]

Before posting this video did you check to see if valve was stiff again Before doing your wriggle trick?

good question, will try that next time!

 

[SJB060685]

I don’t have years of experience like some on here, I’m still relatively young and picking up bits as I go. If the valve is still fluent then that would tell me it’s the head, ie dodgy connections or the motor. Personally for the price of a new valve I’d just replace the whole thing but that’s just me lol

 

[Chuck]

Well this is just sods law, as soon as I say I fixed it, it plays up this evening.

That's par for the course if you use WD-40 to 'fix' a seized mechanism. Will work long enough to confirm the problem but you still need to replace the worn parts and/or use a correctly spec'ed lubriant.

As SJB060685 wisely said just 'replace the whole thing'. Time is money and nobody likes call-backs.

 

[Ric2013]

Trouble is a new head costs almost as much as a whole new valve.

 

[fronty]

Yeah will probably buy valve+head, change head first and plan to do the valve some other time, can't face draining system down again soon as was only done recently.

 

[steadyon]

If the valve itself is stiff but you just change the actuator, you're not addressing the real problem. I'd expect the new actuator to have a shortened life opening and closing a sticking valve.