Drayton mid position valve MA1

[pma]

I'm sure there are many threads on this subject, but none appear to answer my question. Apologies for any duplication.

I have the above mid position valve fitted into my ‘Y’ plan CH system. It was fitted approx 5 years ago and has operated impeccably until very recently.

I can get a situation where system calling for HW and not CH and get the radiators heating up. This doesn’t happen all the time though.

I have checked the wiring to the valve and this is fine.

When I run through the operation, the actuator appears to move as it should do, however the indicator lever doesn’t move as fully over to the ‘W’ stop as it does the ‘H’
Is this normal?

I removed the actuator, and I noticed a slight rattle as if there was something small loose inside the plastic housing.
Is this normal?

At the same time I checked the movement of the valve shaft. Although it appeared smooth and reached a definite stop at both ends of its travel, the movement appeared to be unequal in both directions. If the shaft was positioned with the flats perpendicular to the exit pipes, the movement was not equal in both directions- almost nothing in one.
Is this normal?
Where should the movement be measured?
What amount of movement should I expect?

Thanks

 

[seco services]

in basic terms it sounds like the port may have crud round it or the paddle is damaged in the valve.

 

[cliffa]

My MA1 had started to make the occasional buzzing noise, as though it were having difficulty in changing position. I took the Actuator off to check for free movement in the valve spindle, as I have done before on other 3 ways. Whilst the movement was easy I was surprised how little movement there was and suspected at first that there may be fouling. Searching on the forum here and elsewhere, I didn't find a post that actually said how much movement there should be with this particular valve - only the Honeywell is mentioned in the FAQ. Fortunately Screwfix is not far away so I was cheeky and got them to show me a new valve. I was please to discover that the amount of movement and feel on the brand new valve was exactly the same as on my approx 8 year old one. This type of valve uses just some paddles a bit like on a wind instrument to open or close holes by just a couple of mm. So if it helps any one else with a Drayton MA1 I can say that the movement is again only about 10 to 15 degrees and the flat of the shaft is off centre.