Installing a relay?

[kiwiwonder]

I was thinking of installing a headlight relay when I install one for my electric fan. How do you know which is the power in and power out on a relay and which is the line that goes to the ignition wire so that my fan only runs while cruiser is turned on? WHere is the best place to purchase relays?

 

[Ming89FJ62]

Most relays have a schematic embossed on the side of the relay - you can get one from just about any auto parts store. Most will be rated 20 or 30 amps across the contacts and should cost less than $5. They normally have 5 spade lugs on the bottomof the relay - 2 are for the coil, one is the common, one is normally open (NO) - you'll probably use this one for the lights, and one is normally closed (NC)

Make sure that you fuse your power circuit from the battery to the lights, if you don't and a short developes a nasty little fire could ruin your day.

Harry

 

[theo]

Yep.
Terminals are marked with numbers:
30 - high amp hot lead in for powering the accessory
87 - power out to the accessory (NC)
87A - power out to the accessory (NO)
85 - low amp switched power
86 - ground

I might have the NO and NC reversed. Easy to check with an ohm meter