I know what a diode is used for,but can someone tell me why there is one between the positive and negative post for the 12 volt DC air compressor solenoid?
Thanks in advanced.
Tom,
Most likely a Zener diode. Here is a link to a simple explanation Zener diode - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Zener_diode) and a more in depth version
Zener Diode as Voltage Regulator Tutorial (http://www.electronics-tutorials.ws/diode/diode_7.html)
Pamela & Mike
If the diode is across the 12 volt auxiliary air compressors wires it most likely is there to prevent back EMF (electromotive force) voltages from spiking other items, such as lights and electronics which may be voltage sensitive.
We use a lot of them as Jim said, protect other components from the flyback emf.