Honeywell CM927 & BDR91 heating not switching on or off

[Primus]

Hi,

We have had the CM927/BDR91 running fine with our Vaillant ecoTEC Plus 837 boiler since newly fitted 3 years ago. For some reason over the last couple of months we have noticed that the boiler is not switching the heating on or off when the CM927 sends the signal to the relay box. The boiler is fine for hot water but it wont start/stop the heating.

The Honeywell CM927 looks to be working fine & the battery is not flashing to say change, I have rebound it with the BDR91 receiver just to make sure and the Green light is on the BDR91.

Do I need to purchase a new set or is there anything else I can do to try and get the units working again?

Thanks

Scott

 

[D_Hailsham]

If the green light goes on/off when you turn the temperature up/down, the receiver is receiving a signal from the control unit. If the boiler is not reacting to this then either the receiver is faulty or some other component after the receiver.

Remove the receiver from the backplate then link terminals A and B together on the backplate. If the boiler lights, the problem is in the receiver.
If not, it's after the receiver.

If the receiver is faulty, Contact Honeywell and tell them that the receiver is faulty. They have a good reputation for replacing faulty items, even when out of warranty.

 

[Primus]

Thanks for the quick reply, looking at the BDR91 unit to link A & B do I take the wire out of B & connect it to C?

Also the Green light on the BDR91 is permanently on no matter what we change the temperature to on the CM927. If we take the batteries out after an hour or so the BDR91 flashes Red to say it's not receiving a signal.

 

[D_Hailsham]

Thanks for the quick reply, looking at the BDR91 unit to link A & B do I take the wire out of B & connect it to C?

NO!!

Leave the wires connected to A and B, then use a short length of wire to connect A and B together

Also the Green light on the BDR91 is permanently on no matter what we change the temperature to on the CM927. If we take the batteries out after an hour or so the BDR91 flashes Red to say it's not receiving a signal.

That does suggest that the BDR91 is faulty. However it might be worth replacing the batteries in the CM927, just in case the existing ones are near the end of their life. Use Duracell.

 

[Primus]

Leave the wires connected to A and B, then use a short length of wire to connect A and B together

Well I connected A & B as you suggested and the boiler fired up straight away, I repeated this several times just to make sure. So it looks like the BDR91 is at fault.

Thanks for your help.

 

[D_Hailsham]

Well I connected A & B as you suggested and the boiler fired up straight away, I repeated this several times just to make sure. So it looks like the BDR91 is at fault.

Email Honeywell (link posted earlier) They are closed until 2nd Jan, so don't expect an instant reply.

They will probably ask if you have changed the batteries. (Have you done this?)

What happens if you press the override button on the BDR91? It should turn the boiler on.

 

[Primus]

Will email them for sure.

I did change the batteries and yes if we press the override button the heating works, we just have to control the temperature via the boiler itself, so at least we have heat for now.

 

[Primus]

I tried one last thing which was to reset the CM927 to factory settings and now I keep getting a Fan symbol just above the time on the LCD and I can't find anywhere that tells me what this is.

Any chance you might know?

 

[Primus]

Sorted the Fan symbol issue, turns out that it's the Heat/Cooling setting. To put the CM927 back to Heat mode it just needed the temp +&- buttons held down for 5 seconds.

Thought I would post this just in case it helps anyone else out