Originally posted by Thirteen13
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Car headunit wiring query.. Calling all electrical guru's!
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Going off your wiring description, the pins on the relay are irrelevant for the diode orientation (assuming you have the two correct pins for the coil) the cathode of the diode should connect to whereever the blue wire from your head unit connects and the anode should connect to the black wiring.
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As the magnetic field around the coil collapses when the relay turns off it induces a current in the coil, resulting in a negative spike (generally in the vicinity of -400V) back into whatever is driving the relay, depending on what the headunit uses to switch the remote output this sort of back EMF may quickly kill it, by placing a reverse biased diode across the coil provides an alternative path for the spike, thus preventing it from damaging the drive electronics.Originally posted by artman View PostIf all you are wanting to to do with your head unit remote turn on wire is trigger the relay, wire this wire to one side of the relay coil, the other side of the coil to earth. The relay coil doesn't have a polarity
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i ran 3 amplifiers off a 30A bosch relay and just used the remote trigger wire from the head unit to switch the relay on. ran that setup for about 1.5 years and never had a problem, still using the head unit now on a much smaller setup (one amplifier) and have removed the relay and just use the remote trigger from the head unit straight to the amplifier. still works fine.
a Pioneer head unit like yours isn't easy to kill, i don't think you'll really need the diode, but if you want it then go ahead.
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