Having just driven my new Fiesta for the first time at night this evening, I have found the instrument cluster to be too bright. Anyone know of any way of dimming this area?

Unfortunately, there is no switch to do this. It is a feature which I miss having as I also find the dials too bright sometimes.

You would have to wire in your own variable resistor to the interior lighting circuit.

I know that it does this, I was just wondering why you'd use this when a perfectly ordinary audio cable would the exactly the same thing.

Exactly what I was thinking, it wont transfer data nor charge just the audio