[X-posted from heating forum because there's more traffic through here :wink: ]

Good grief, there's a forum for everything!

Right, I hope someone out there can help me. We have a heating controller that runs a domestic Indux ducted MVHR and heat exchange system. According to the controller, we have 4 temperature sensors - 3 internal and 1 external. Since a thunderstorm last year, the controller keeps flashing up that sensor 4 (the external one) is faulty. In spite of this, the system appears to work and heats our house and circulates the air as it should.

In all the plans that were left me by the previous owner of the house, there is no indication of where this external sensor is. We have had service engineers out to service the heating system but they could not clear the fault nor find the sensor. The engineer has had a look over the outside of the house and also in the air intake ducting (which is where he would expect to find the sensor). So there may not even be an external sensor fitted; the controller just thinks there is.

Surprisingly, there is no indication of who manufacturer of the control unit is - it just says "802 controller" on the front panel and the photocopied instruction book for the controller also has no manufacturer details.

This instruction book doesn't give any indication of how to clear the fault message, either.

So, is this controller unit familiar to anyone? If so, would someone be kind enough to tell me how to clear the fault? And, if anyone has any experience of these things, where should I look for an external sensor, if one exists?

Thanks in advance.