Cental Heating Issue

[F4ranky]

Hello to all.
Central Heating cooled down a few days ago, the diverter valve Drayton ZA5 controlling central heating appeared malfunctioned.
I have tried to operate manually but did not remain on.
I removed its head and turned the central heating on by opening the valve manually whilst Hot Water, HW valve on.
CH does not turn on with HW
I checked connection of the diverter valve, it looked connected without any obvious and visible faults. I thought it was faulty and disconnected it. I found it operating when I powered to its brown and blue leads before replacing it.
I retuned to the junction box and found no power at the terminal of the brown lead when boiler is commanded for CH.
The CH appears on screen of the programmer as CH is turned on.
Your professional and expert advice for this issue would be appreciated.

 

[cross thread]

Have you a room stat ?

 

[F4ranky]

Yes there is a thermostat. I have tested the junction box with thermostat on ie maximum temperature position.

 

[cross thread]

Have you tested continuity through the thermostat

 

[F4ranky]

No,I haven’t. Would you advise me what is the best process to check the continuity of the thermostat please.

 

[CBW]

Turn power off, use a multimeter set to continuity and turn thermostat up, make sure that the switching receives continuity.
I would possibly check voltage rather than continuity, again with the meter, or a 2 pole voltage indicator, make sure voltage is being sent from thermostat switched live, and then test at terminal strip in wiring center.

 

[F4ranky]

I am pleased to let everybody know that I have resolved the problem successfully by using this platform.
CROSS THREAD & CBW who have jointly guided me to root cause of the issue and how to check it respectively. There was a Loose connection to an oxidised live lead to thermostat from the junction box.
I am sincerely grateful to both of the above mentioned members equally but in particularly to Cross Thread who point out me to the right direction to troubleshooting.