Have you checked for interfearance? If the motor will just go forward with no control- that ushually means the relay has welded itself shut, try giving it a tap with a screwdriver or somthing just to shake it loose- if that doesnt work replace the relay. I had that problem a few times with my old 15amp CPUs.

Ive got one 30amp exsternal relay- bought from brand new, When i wired it up (correctly) it did nothing- dead, Never got it working- should probably send it back to electronise,
Any idea what could be wrong with it? Batterys were at full 24v, Motor works- r/c was fine (tested with the other speedo and a servo)