3-port motorised valve problem

20 Mar 2005
Reaction score
United Kingdom
Honeywell 3-port motorised valve, Danfoss cylinder stat, Danfoss room stat, Ideal Elan 2 boiler, Randall Set5 programmer. System working fine for a couple of years (since I moved in).

Hi all,

Problem: HW was working fine, but no CH. Moved power head on motorised valve to open position using manual lever and CH works again!
Decided synchronous motor was to blame so changed it (generic motor £10 from local plumber's merchant). However, still no CH without using lever on power head! Tried all possible permutations of CH and HW demands but nothing causes the valve to move from its "off" position (just HW working).

To complicate matters, when the valve is in "off" position (ie. spring has pulled it back), and I put the CH on, no movement occurs. However, if I manually move the valve to the mid-position (using the lever), and put the CH on, the valve moves all the way to the position furthest from "off" (240V is seen at motor). Does this mean one of the micro-switches is broken? If so, any ideas which one?

Thanks for any help!

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does the switch live at the room thermostat show the appropriate voltage when ch is calling and you turn the room stat up and down?
OK, thanks for the replies. I got the multimeter out and took the power head apart. Checked both the microswitches and one wasn't working. Just replaced it with a new one from Maplin's (£1.49 off the shelf) and things seem ok once again!!

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You've got me...if it don't motor across the fault is before the microswitch, perhaps you were lucky.
Oh dear - looks like my "repair" wasn't as successful as I first thought.

So, time for a new valve head. The current one is a Honeywell 40003916-003 and can easily be removed via the two retaining screws. Any ideas for where I can obtain a cheap replacement please?!? Am I correct in thinking that a new Honeywell 40003916-003 will fit straight on (ie. they haven't changed)?


PS. Tried to check Honeywell site but it's down at the moment.

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