I've just been out to the car park and tried it again. The roller worked in one direction for a little bit then eventually stopped. Hijack is showing the measured value to be 4a (The other way is 5d I think), but like I said after a couple of minutes it stopped working.

The source selection button does work if you hold it down for a couple of seconds (like you mentioned in the thread), this shows up as a reading of 0. I'm thinking about wiring a resister in series to try and bump up these readings to see if I can get it to work any better, anybody have any ideas?

Thanks.

Adrian