The problem we are having with our central heating seems to stem from the Honeywell 3 port valve. In the summer with the heating off and water on the upstairs radiators get warm.
In the winter SOMETIMES the last radiator in the loop stays cold until the water has heated sufficiently for the cylinder stat to turn water heating off then it warms up straight away.
Looking at the valve postition, there would appear to be only 2 postitions the valve operates in - heating only or mid position heating and water.
With water heating only the valve doesn't move on the springs away from the mid position.
I have checked the wiring from the valve and all would appear to be in order but for 1 thing, the water only state.
I have a live current on white!!!! This I know isn't correct. Upon further investigation I note that if I disconnect the wire from the thermostat that connects to the white, then the white lead is still live!!!!! This to me indicates a fault with the circuit board.
If I take the valve head off, the spindle moves with a pair of pliers but only by a very small amount, maybe 10° each way.
With the head removed the valve motor moves quite a lot further and returns on the spring.
Any ideas on this. Thanks.