I would like to know how to hook up the LEGO 2838 9v motor. I understand that the Power Functions extension wire is compatible with the 9v system, but how on earth do I wire them up?
To wire 2838 motor, you have to use one PF extension cable, one end connected to PF power source (either battery box or IR receiver), the other end has a 9V compatible plug on bottom. Unfortunately, 2838 also has its connector on bottom, so you also need a 9V cable (such as this one) to connect them.
1You could also use an extension plate (2x4 or 2x8) underneath the motor, so that you can plug the PF extension cable on it.– JoubarcNov 21, 2014 at 12:37