The wiring is :-Stat com to yellow wire (programmer) water on.
stat sat to programmer yellow/green, valve grey.
stat call to valve orange and boiler white.
I think this is the same as your example. I am not sure that Call is on the right terminal in the wiring box
my boiler is a potterton Prima C open flue using a Towerchron QE2 programmer.
How have you checked these cables connect as stated? On paper they all look correct.
The boiler white wire should connect to the SwL (middle) terminal on the boiler.
Do you have a multimeter, if so you can check the voltages on the terminals as follows:
Notes
The terminal nos assume the standard Y Plan wiring.
The pump will not be connected as shown. This is because you have pump overrun. It will either be connected directly to the boiler or to a spare terminal which then connects to the pump terminal on the boiler
Carry out tests in sequence given.
CH Only Test (Port A open)
Turn Power OFF at main connection for the system (turning CH and HW OFF at programmer is not sufficient) This resets the valve to rest position
Disconnect white valve wire from terminal T5 and grey wire from terminal T7.
Connect white and grey wires to permanent Live (T1)
Turn Power ON
Valve should move over so port A is open and boiler light (check by feeling that only the pipe from port A gets hot)
If the valve does not move, Switch S1 is not moving over.
If the valve moves but the boiler does not light, switch S2 is not moving over. (check 240V on orange)
HW Only Test (Port B open)
Power OFF (valve returns to rest position)
Turn HW stat to lowest
Disconnect grey and white from permanent Live (T1) and temporarily make safe (e.g connect to spare terminals in the wiring centre)
Disconnect cylinder stat Common from T6 and connect to permanent live (T1)
Power ON
Turn cylinder stat to max.
Boiler should light. (check by feeling that only the pipe from port B gets hot)
If it does not light, the cylinder thermostat is suspect (check for 240V at Common and Call terminals of cylinder stat and at terminal 8 ).
CH and HW Test (Ports A and B open)
Power OFF
Turn cylinder stat to lowest
Disconnect cylinder stat wire from permanent live (T1) and reconnect to original terminal (T6)
Disconnect white wire from temporary location and connect to permanent Live (T1)
Power ON
Valve should move to mid position
Turn Cylinder stat to max
Boiler should light (check that pipes from ports A and B both get hot).
If boiler does not light cylinder stat is faulty
Power OFF
Reconnect white and grey to original terminals (T5 and T7)
Turn HW OFF and CH ON
Set CH stat high
Turn Power ON
Valve should move to Port A open, boiler light and Port A get hot.
Turn CH OFF, so boiler goes out.
Boiler should go out but valve stay in CH only position
If boiler does not go out, check voltage on orange wire.
If orange has 240v, the actuator is faulty
If orange has 50-150v, there is a problem with the boiler
If these tests are passed, the problem is elsewhere.
Testing other components
Cylinder thermostat: disconnect wires from CALL (1) and SAT (2) terminals when checking, this prevents false readings due to back feed.
There should be 240V on Call (1) when stat is turned up and 240v on Sat (2) when stat is turned down
Room thermostat: disconnect wire from Switched Live when checking to prevent false readings due to back feed.
There should be 240v on Sw L (3) when stat is turned up and 0V when it is turned down.
Note: you may find that terminals 1 (live) and 3 (Sw Live) of the thermostat have been swapped over. This is not too important for modern digital thermostats but should be corrected if you have the older mechanical thermostat.
Programmer: Check voltages at CH ON, HW ON and HW OFF terminals when programmer set to appropriate positions. Also check the voltages when the timer is used to switch on/off.
