Published 2007 Updated 2013
Wiring A Relay
Recently I found the need to rewire my cooling fan on my stroked 1600. I was not quite sure how to approach this as I am not a very good electrician. I do many things well but electrical things not so well. I remember TR once told me you could grab just about any relay from a parts car and make it work. Well, I did not have time to run up to the Pick-N-Pull so I opted to buy a new one. My fan draws around 20 AMPS or so at start up so I was looking for a 30 AMP relay. I searched online and found way too many choices. I decided to try Summit Racing to see what they had. Low and behold they had a general application 30 Amp relay that fit the bill exactly. It even came with the wiring harness which is a real plus. I ended up ordering VIA-80237-Relay, Starter/General Use, 30 Amp, Single Pole, Each Price $5.95 plus shipping. This is a Bosch style relay which makes the layout very easy.
Wiring it up was pretty easy as demonstrated by the below sketch. Your mileage may very but it worked out fine for me. Just make sure you have really good grounds because poor grounds are the root of many electrical problems.
A few notes: You can use relays to power many devices-fog lights and cooling fans are just a couple. You can use ATA inline fuses, circuit breakers, fusible links to protect your circuit. I chose to use a rocker lighted switch but you could use a flip switch or a toggle switch with an independent light if you like. The way I did wire up the relay should work for most applications. Good luck with your project.
Here is some additional information you might find useful regarding relays-thanks to Craig Erwin.
YouTube video describing: Electrical Relays – How To Wire
You need to right click and open link in a new window for this to work
http://www.youtube.com/watch?v=JkG22KgciwY
HEADLIGHT RELAY DOCUMENTATION USING INDUSTRY STANDARD RELAY LABELS
Power wire to relay (30)
One wire out to each light (87)
One wire from switch original harness to relay (85)
One wire to ground (86)