I have an MC21 engine in my MC18 and and had connected the neutral wire from the GPS (red/green) to the neutral light wire from the loom, so I can get the neutal light to work with the 21 engine. The light would'nt come on, so I remembered that the neutral switch on the 18 acts an earth to the engine. I connected the red/green wire from the GPS to the engine block, and the neutral light came on , unfortunately now however when I go through the gears it won't go off Any ideas?