It has four solenoids, one has a small resistor, one has a large resistor, one is the forward solenoid, and the last one is the reverse solenoid. I have checked all of them and they all work, as soon as I turn on the key the solenoid with the large resistor kicks in and I believe it never goes off, If I unplug the speed control it goes off but when I plug it in it comes back on. I ohmed out the speed control box and no matter what I did I couldt get the ohms to do anything other than OFL or 132 ohms