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What does pin 87 do in our relays?


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Looking at wiring diagrams and reading other posts, I thought I knew what I was doing ;-)

I thought relay 87 (say in the radiator fan relays or the engine compartment blower relay) went to the positive end of said motor. And if the DME wanted to turn on said motor it would send +12V thru pin 87. i removed the engine compartment fan relay, and supplied +12V (from the cig lighter) to see if the engine compartment fan would spin. It didn't and I blew the cig lighter fuse. fuse replaced, no harm done (cept my ego). How do relays work? what is the purpose of each pin (specially pin 87?

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Radiator fans are on a 40A circuit.

Cigarette lighter is a 15A circuit.

Now you know why the fuse blew.

You need to look at the schematic - the relays turn on fan motor at either normal speed or high speed - one through the ballast resistor and one not through the ballast..

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Ah yes, 15 < 40. ;-) now I don't feel so bad. But am i right that there seems to be some kind of a standard and pin 87 of most relays go to the +12V of the thing they turn on? I plan to connect pin 87 of the engine compartment blower relay to pin 87 of the left, stage 2, radiator fan. i want the engine compartment fan to turn on whenever the high speed rad fan turns on.

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