Thanks for the suggestion, a tad over my head, but I think I follow your drift.

Darrel / Steve,
I've noticed that if I advance the pot fully (thus taking the A/D input pin to supply) and then turn it back down the loco stays at full speed, and the only way to correct this is to disconecct and reconnect the supply. - any suggestions (could this be down to the wrong setting for ANSEL)