RELAYS

Basic Relay Hookup


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SCHEMATIC FOR HORN RELAY
The numbers assigned to the terminals seem to be an industry standard. They are usually stamped on the top or the bottom of the relay - sometimes both. All that matters is that you know which pair is low current and which is high current. The relay doesn't care which way the current flows. You can use an ohmmeter or a 12 volt source to check this. You can't hurt the relay if you only hook up one side at a time. The 2 terminals 'facing' each other should be the low current ones. They should be numbered 85 and 86.An ohmmeter across them should show (according to the diagram) a resistance of 66 Ohms. If you put 12 volts across them you will hear a click. That is the noise of the high current 'switch' part of the relay closing. The 2 terminals across from each other but at 90 degrees should be the high current terminals. They should be numbered 87 (may also be 87A) and 30/51. If you put an ohmmeter across them it should show an open circuit (infinite ohms). If you put 12 volts across them nothing will happen. No click. And no current because the relay isn't 'on' so you can't blow the battery.
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TYPICAL HEADLIGHT RELAY TERMINAL LAYOUT



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