Vaillant Ecomax - Danfoss 51RF/RX1 = Help Please

[Spleurker]

Hi,
My parents have just moved house. Their new home has a Vaillant Ecomax combi boiler, which was fitted in 2004. The central heating side of things is controlled by a Danfoss 51RF wireless thermostat. My Dad couldn't get it to work.
I managed to download a manual for the thermostat, and followed the instructions to reset it to the RX1 receiver. I checked the functioning of the thermostat was controlling the boiler and left them to it. However, the next morning, the thermostat wasn't controlling the boiling again. I oncve again set it all up. My Dad has just rang to say this morning it had gone off again.
Is there something I'm missing. Is there any reason for the thermostat to fail overnight. Is it something to do with the boiler?
The HW is always working fine.
Any tips will be gratefully received.

 

[simond]

Suggest you temporarily link pins 3 and 4 inside the boiler. This will call for permanent heating.

If the boiler does not fail in this instance you have proved the fault onto the stat. Does sound like the stat to me, PS:if you have a multimeter you could check it out without doing the aforementioned.

 

[Spleurker]

Thankyou

 

[gas4you]

Check or replace the batteries in the sender unit.

 

[Spleurker]

Cheers for the replies.
It always pays to check the obvious first.
The batteries in the sender were low, a new set put in and all seems to be well.