David wrote in news:g8rj75Fh0nmU2
@mid.individual.net:

As discussed previously I suspect I have a fault in the 3 port valve.
Drayton Mid Position Actuator MA1.

For diagnostics, do I have to do more that check that when CH is called
for by the programmer power goes to the thermostat, and when the
thermostat clicks on power comes back to the valve?

I am assuming that the sequence at the valve is:

(1) CH request from the thermostat

(2) Mid port valve moves to open CH port

(3) Controller then calls for pump and boiler

This has the second assumption that if (2) fails to happen then (3) will
not happen (which seems to be more or less what is happening).

Diagnostics day tomorrow, hopefully.


Cheers


Dave R



The call for the pump and boiler comes from the switches in the valve as
far as I know.