Vaillant VR65 eBUS output drop to 1.9v

26 Sep 2023
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United Kingdom
Hello, I have a Vaillant EcoTEC plus624 boiler (2010 model), a Vaillant VRT392 thermostat, and a UniSTOR hot water storage cylinder connected to a Vaillant VR65 control center, now the problem is the VRT 392 suddenly stopped working which is completely dead, althrough I still have hot water but cannot control central heating without the thermostat.
I measured eBUS output from the boiler is 21.67V, but it comes out only 2V from VR65, which the VRT 392 requires a voltage between 9V-24V to operate, I need to ask if anyone knows whether the VR65 developed a fault.
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It sounds like it. If you need heating, are you able to join the 2 wires together in a connector block and alter the temperature at the boiler temporarily?
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