Three port valve or thermostat

[dishman]

Just doing a bit of problem solving.

The boiler, which has bee fired up for the first time for winter, initially hand an issue which I traced to the three port valve. It is an open vent, fully pumped system and it is a Honeywell valve.

Just to get the system running, I have set it to manual for the moment, which is not very efficient.

When I set it to manual, there is motor resistance pulling the lever back. It pulls back by itself if I do not lock it to manual.

When I call for central heating when the valve is set to auto, nothing happens. The pump does not run. Yet, the manual/auto lever on the valve goes loose (no resistance) when I call for central heating. This (I assume) means the valve has moved by itself already? Does the arm normally move (or can you see it move) in auto mode?

So, if the valve is moving, but the pump does not activate when central heating is called for, does this suggest it is the thermostat that is at fault and it is not calling for heat and activating the pump.

When I request hot water, the pump starts straight away. This is the only way to heat the house (with the valve set to manual at the moment).

Many Thanks in advance....

 

[D_Hailsham]

Do you have a multimeter (and know how to use it)?

 

[dishman]

Not to hand, I was thinking of that to test the valve......

Any other method to test or theory as to possible cause?

 

[D_Hailsham]

Mid-position valve operation and fault finding may help.