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Old 02-05-2013, 07:42 AM
DanielC DanielC is offline
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This relay, available from Summit Racing has two 87 terminals.
Handy for wiring two headlights to one relay.

Because of the diode in some relays, keep pin 86 positive, and pin 85 negative. You can switch either coil feed wire, that does not matter.

The relay you use may not have a diode in it, but there is a possibility you may need to replace the relay at a later time, or the next owner of the car will. If you wire the coil of the relay with the wrong polarity, you have to make sure the relay you replace it with also does not have the diode.

The diode is used to suppress inductive kick back. Just like the primary side of the ignition coil, when a relay coil is switched off, the magnetic field collapses, and that induces a brief high voltage spike in the relay coil.
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