| Author | Message | ||
| Charles T (Charles)
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Thanks guys. | ||
| '75 308 GT4 (Peter)
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I posted this diagram here before, it is a typical 5-pin relay. As Ben writes, the electrical output from a headlight switch would activate the relay coil by connections "85" & "86". The coil throws an arm that connects the "87" pins which allows greater current to flow to the high current device (ie: headlights). "30" is the connection recieving + power from the battery.  | ||
| Ben Lobenstein 90 TR (Benjet)
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In short a relay is a switch. Relays usually act on a remote signal to operate. Let's see if I can completely confuse you with a full explanation. Think for a moment about headlights. Usually they have a 15amp relay, and 15amp capable (heavy gauge) thick wiring to the bulbs themselves. There isn't enough room to run that thick wire up your steering column to the actual headlight wand. Also think for a moment about how many of these wires you would need to run everywhere (low beams, high beams, wipers, horn, etc.). So a small voltage (thin wire) runs to the actual headlight wand on your steering column. This low voltage is the signal to the relay to activate or de-activate the main power supply that runs power from your battery to your headlight harness/bulbs thru your fuse panel. Once the relay sees that you have activated the remote control it makes the actual contact between the power source and the headlights (or whatever you are powering). It also does the reverse when you turn things off. I may not have given the best possible explanation, but hope that this helps. Let us know if you need more help. -Ben | ||
| Charles T (Charles)
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Alright guys, I'm showing my ignorance here. What is a relay? What's if for? And, how does it work? Can anyone give an example on what it does /protects and how (i.e., light relay, fuel pump relay)? Thanks... Charles |