[Al Skierkiewicz]

All,
I did forget to mention that diodes are used as spike suppression. They are wired in parallel with the solenoid coil and the cathode (banded end) should be connected to the side of the solenoid connected to the positive terminal of the battery or the plus output of the Spike.
LEDs can be used as diodes except that LEDs have about a 2 volt drop across them as opposed to 0.6 volts drop of the average silicon diode and they cannot handle high currents. When diodes fail they usually short so having a shorted diode across a solenoid would prevent the solenoid from operating.