Climate control died

[Tomdownunder]

Yesterday I hopped in the x5 and the inside fan was blowing full bore and nothing was lit up on the climate control. I pushed every button and no change. I got to work and turned the vehicle off, took the key out of the ignition and fan still going full bore.

I opened up the back and disconnected the battery while I was at work.
On leaving work I used a jumper pack on the terminals at the front to open the tailgate, reconnected the battery and headed home with fan again going full bore (hot air on feet, outside air from top vents). Disconnected battery again once home.

I had a previous problem with the climate control where I had every light on every switch light up and nothing worked and so climate control panel was replaced with second hand one about 3 years ago.
This morning I swapped the old one for the newer one to see if the fan kept going and lo and behold, no fan just all the lights on.

I then swapped the front panel with the screen from the newer one to the older one and fault remains the same (all lights on). The newer on with older front still made fan go full bore.
By swapping the control units I think I have eliminated the final stage resistor as the culprit (replaced that 3 years ago also).

Do the control panels regularly die or am I just unlucky, or is there a possible other cause.