I don't have your email address but I could do with some more help.
Not sure if you remember my earlier posting:
Anyway, I've ripped the house apart sorting this out, found several
problems but no huge ones...
Ignore my earlier remark about the rads, the plumbing is fine, it
crossed beneath the only floorboard I couldn't lift :(
So, the rads downstairs were cold in the middle so I drained the
system and flushed them out with a hosepipe and a lots of waving the
rad around in the garden.
The donkey that did the plumbing put my drain tap at shoulder height
(above boiler) so when I drained it I only drained the upsatirs and
had to do the downstairs from the pipe I disconnected from a
downstairs rad !
Might have to adapt this in the near future...
I've got a room stat from screwfix so I can control the CH better
(once I've fitted it), but I still get scalding HW when the system is
switched to CH only.
I took the valve head apart, with no power, the valve returned by
spring to the position I assume is port B open.
switched power on - the valve remained at same position.
switched to HW only - the valve remained at same position.
switched to CH and HW - the valve moved very slightly (about 10deg of
rotation ?) - should be point AB
switched to CH only - the valve remained where it was !!! should go to
point A !
I did these test with the CH cold and the HW warm and played with the
tank stat to get the correct HW ON /OFF level that I required to test
it, all the signals to the valve operate as expected i.e. the room
stat and the tank stat are both switching over OK.
**** heres where I need help ****
So it seems the valve is not travelling to position B. Hence my HW is
scalding and the stat tries to shutoff the HW but the valve isn't
blocking port B to give port A only, but where is the fault ?
Is it the head unit (that I can replace) ?
Is it the actual valve, can I strip it and clean it ?
Do you get the entire head assembly (microswitches & motor) as
My valve is marked "Head replacement 40003916-003
It looks like it's the whole thing:
But what is this, is this the innards of the valve ?
"272742A CARD Replacement ball and ‘O' ring kit for
V4043, V4044 and V4073 valves."
I've ordered some stuff from screwfix, but I don't want to use it
until I know what the problem is and if I will have to drain the
16307 CENTRAL HEATING SLUDGE REMOVER 1 LTR
13162 CENTRAL HEATING INHIBITOR 1 LITRE 1
Many thanks for your time and effort,
email addr is OK if you want to reply direct: for_q2 firstname.lastname@example.org
P.S and Merry Christmas whilst I'm at it ;)
Remove the head from the valve. Now try turning the valve position with
pliers. If this is easily achieved, then the head is the problem. If it is
stuck, then you may need a new valve. It may be possible to replace just
part of the head, but this requires time to diagnose which part is wrong.
You can get replacement switches and synchron motors easily enough.
I have no idea if you can service the valve portion. However, at 30-40 quid
for the entire thing, I wouldn't bother.
I did try to turn the spindle with pliers but it was rock solid. But when I
reassembled it and watched the motor turn the spindle it seemed to turn to
position AB OK, so I figured that it was meant to be stiff and it was a
However, I'm not sure about it now. I thought a Honeywell v4073 was more
like £70 than £30 ?
£30 for the replacement head ?
Well, actually looking at the figures, I wasn't thinking genuine Honeywell.
You can get (from Screwfix inc. VAT :
Horstmann 3 port = 35.99
Danfoss 3 port = 44.99
It seems the Honeywell is a touch over 60 quid, though, from discounted
heating. Myself, I prefer S plan and 2 port valves, anyway, as I like to
Given this situation, you may well have knackered the gearing assembly
in the head.
It would be far preferable to replace the whole thing and be done with
The Honeywell V4073 lists for around £70 but you should be able to get
it discounted down to around £55.
Discounted Heating have them for £62 inc. or other good makes for a
few pounds less.
To email, substitute .nospam with .gl
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