I don't know if the warning lights on the 750 are the same as the 400 or not. Try looking up a wiring diagram. The oil pressure and neutral lights on mine are fed power through the ignition switch and the light comes on when the sensors close and complete the ground side. If you have a test light, check for power at the lights with the ignition on. Both lights may get their power side from the same connection. It could be loose and causing a problem with both.