Honeywell 3 port valve issue

[Thecasementkid]

Hi guys,

A few months ago I upgraded my room thermostat to a CM67 and boiler timer control to a ST6400C Programmer.
The system seems to have gone haywire, but the wiring I believe is correct. (I took pics to compare the wiring before and after).
With the HW only on via the boiler timer, the rads get hot. With both CH and HW on via the boiler timer the rads get hot (even if the HW only is activated by the cylinder thermo). The room thermo can be off with the HW on and the rads are hot. Could the 3 port valve be playing up? I can hear it ticking which it never did before. Any advice appreciated.

 

[gas4you]

Yes the 3 port valve would be the first thing that I would test.

 

[MANDATE]

sounds as though the valve is stuck at mid point.
I would see if the actuator head can be removed off the valve spindle and check to see if the spinde is easy to turn between finger and thumb.
The room stat when calling for heat, makes the 'white' wire of valve live, this in turn drives the valves motor until it triggers micro switch No 1 at mid point.
At this point it depends if the 'grey' wire is live or not.
If not the valve stays at mid point.
If live the 'grey' drives the motor to CH only.

If room stat is off or not calling for heat, then 'white' is not live' so motor would unwind due to return spring, back to HW. Yours does not appear to do this.

 

[D_Hailsham]

Honeywell Wiring Guide has detailed fault finding instructions for a mid-position valve on pages 14 and 15.