Replacing a VRC430f External Temperature Sensor

24 Oct 2017
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United Kingdom
I have had a Vaillant ecoTEC boiler with the VRC430f Weather Compensating Controller for several years without any serious problems. Recently, the external temperature sensor has been showing 18 or 19C, so the heating is not doing a lot.

The Signal Strength screen in the VRC's Installation Assistent (sic) says the sensor signal level is 0, but it didn't say to Clean the sensor, so I'm guessing it is getting some signal.

I figured the sensor is faulty, so I got a new VRC430f from eBay (couldn't find the sensor on its own anywhere) and have replaced the old sensor with the one in the new set. I started it up, the green LED flashed for a while, but the VRC is still saying the signal level is 0. I set Learn Mode to ON, but that didn't seem to make a difference.

So, my question is, do I just wait or do I need to replace more than just the sensor with bits from the new set? Are the part IDs linked digitally or some such? I was hoping they'd work together with only minimal fiddling from me.

The system was installed and is maintained by British Gas, but the engineer said he knew nothing about it and could do nothing apart from replace it with a simple timer...

Thanks for any suggestions!
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A quick update. I read a separate thread here where there was a suggestion that the outdoor sensor had condensation inside. This is quite possible with the amount of rain we have had! I had the sensor indoors for a few days, so it had a good chance to dry out. I had been totally unsuccessful in getting the VRC to recognise the replacement sensor, so I just put the old sensor back outside and, a few minutes later, I had a 10C outside temperature. Better than 0 or 19C!
The system was installed and is maintained by British Gas, but the engineer said he knew nothing about it and could do nothing apart from replace it with a simple timer...

They can sent a more technical person to sort out your possible fault,just ask them.

Remember they fitted it and took the complete installation on a service plan,if they mentioned they do not cover some parts of the installation,please excuse me :)
Thanks for that. I don't remember them saying that some items were not covered, but they can change the rules when they like and there isn't much we can do about it.

The sensor seems happy and I have a good signal coming from it - 6 through the wall - and that's better than the receiver in the boiler.

I was thinking about getting a vSMART controller installed, but I'm not convinced getting the outside temperature from BBC Weather is better than a finger in the air. They often differ by a few degrees. I use the sensor figure to decide if I need extra clothing when taking the dog (not the one on the left, who passed last year) to the park in the early morning. Of course, that can't tell me if it's raining!

Thanks again.
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Just to wrap this thread up, the old sensor went faulty again after a day or two. I bought a new VRC 430f controller set on eBay. The old controller wouldn't recognise the new sensor, so my best guess was that they were digitally connected. The British Gas engineer has just been this morning to swap out the old set and put in the new ones. Boiler off and all old bits unplugged.

New base station into the boiler first, switch on, red light.

Batteries into the new wall controller and external sensor on the wall outside.

Signal strength figures and temperature sensor readings now non-zero and the light on the boiler has gone green.

All set up and working!

Thanks for all suggestions.

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