Honeywell v4073a - new motor but still playing up

[Diggory]

Hi all – wondering if someone may be able to help diagnose a problem with Honeywell v4073a mid position valve. Have checked the posts but still struggling.

Problem
It has been in place working fine for about 8 years [I replaced a switchmaster valve – rest of control system is still switchmaster]. I am now getting ALL the rads hot when programmer set to HW only so obviously good amount of by-bass going on at port A. Assumed that the motor had gone so replaced it [£20] using the Honeywell kit but problem still exists

Have now bought but not fitted a complete new v4073a at £57 with intention of swapping the power head first [save a drain down]. Looking at the new valve the default position seems to be port A closed. I have done a cursory check of the faulty one with an AVO [need to do this properly when I have the colours and volts] and seems that in HW mode it is getting a no volts signal [orange is always live but guess that is boiler and pump on]. What I don’t understand is why it doesn’t then close port A by spring tension. When I switch to CH+HW I get live on the white wire so programmer and stats are talking to it.

I am trying to figure out if the fault is electrical in the powerhead [micro switch / diode] or if it’s a mechanical problem within the valve body.
Any tips for diagnostics or from experience with this fault much appreciated. Thanks D

 

[twgas]

remove actuator and check spindle is free to move, the removable heads have a dimple on case and only 2 screws securing it.

 

[namsag]

If the valve is passing changing the head won`t do diddly valve body needs changing

 

[D_Hailsham]

Read How the V4073 Mid-position valve works. You will then know what voltage to expect on which wire and when.

 

[Diggory]

Thanks all for advice

Twgas:Will remove head and check spindle turns okay
Namsag: Take your point

Suppose I was hoping for a mode of electrical failure that would cause valve to hunt or hold open rather than mechanical failure within valve body. Do the valves themselves often fail like this. Have kept system relatively clean [DS40 and well flushed three yrs ago] and always run with fernox + bacteria inhibitor. Have not needed many drain downs so only min amount of hard stuff from water. Is 8 yrs all I can expect from one ? Thanks D

 

[Diggory]

Guys - wondering if my ball has come off

Removed power head and checked spindle as you suggested and there was a definite tight spot approaching port A (CH). Gave it a gentle wiggle with fingers back and forth few times until felt free. Refitted power head and tried again – no joy still passing

Carefully removed head without disturbing spindle and it was stuck a tight spot so gave it another wiggle finger and thumb [nothing excessive]. It moved, more than I think it should – would say that there is more than 90 degrees of angular rotation on the spindle (and I suspect more movement is there if I tried !). I cannot see how this could happen unless spindle is turning in cranked ball arm or has come off – has anyone seen this happen; do they come off ?

If I have to fit a new ball / arm assembly am wondering if one of the adaptor plates designed for pre dimple valves will fit mine. Looks easier to avoid disturbing the 3x22mm compression joints and lift the valve plate to repair / replace ball and arm. Plus cheaper than replacing whole valve. Anyone done this ?

Welcome your thoughts - thanks D

 

[Gasguru]

Just fit the ball and plate (and O ring) from the new valve body you have.

 

[ChrisR]

Yep, I've broken them off too!

 

[Diggory]

Thanks both

Gasguru - yep did think about that but just seem an expensive way to get the ball and plate [£57] when adaptor plates are less than £10

ChrisR - glad not just me then. If the ball or ball and arm have come off spindle assume that they cannot escape the valve body and get stuck somewhere else ?

Cheers D

 

[namsag]

For the sake of £60 quid tight a#s change the valve less chance of compression fitting leaking than changing plate etc then its all new