Central heating not working

[QPRJohn]

I'm trying to diagnose a problem with my friend's CH.

It is a conventional gravity fed system, controlled with a Honeywell ST9400 programmer in conjunction with a HCW 80 room thermostat and HC60NG relay module.

The hot water side of things works normally.

I've performed the "teach in" between the room stat and the relay module several times, the green led operates on the module when the room stat is triggered. I can hear the relay operate in the module but almost immediately it sounds like it has switched itself off.

I have checked the three port valve by moving the slider to the end of it's travel, it only appears to go half way back? If I hold the slider in it's fullest position, when I operate the room stat the pump will also only work momentarily with the relay switching on and off.

Could the problem be the three port valve?

Thanks

John

 

[twgas]

Do you have the means for safe electrical testing?

 

[QPRJohn]

Yes, I have several meters.

 

[twgas]

check for mains power on the white wire to the valve, when there is a call for heating .

 

[QPRJohn]

Ok will try this and get back to you. Thanks

 

[QPRJohn]

My meter is DC, I'll borrow an AC Meter and get back to you.

 

[QPRJohn]

No feed to the white wire.

It is fed momentarily when relay cuts in and then out.

By linking a 240v feed directly to the white wire it operates the valve, so from that I assume it's the room stat or the relay module or both!

 

[twgas]

Sounds like you need a new receiver.

 

[QPRJohn]

Thanks for your help Mick.