Relay wiring

[4x4mike]

I have a quick question and for some reason I forgot. A little back ground for later searching if it's needed. Assuming a regular 30 amp, 4 prong automotive relay:
Prong 30: Fused to battery
Prong 85: Ground
Prong 86: Switched 12 volt, ignition
Prong 87: To accessory


My question is about prong 86. On my old truck I had multiple relays wired for various devices. I used a small junction box for the switched 12v and tapped into it when needed. I had lights, compressor, etc on it and it was always fine. I forget where I got the switched power from but wanted to make sure on the 4runner. This "leg" of power to the relay is the low draw side, correct? I thought it was but on the schematics I have and find on line call this leg the load. I don't want to overload whatever I plug into. I don't plan on pulling more than 30 amps and for the time being I will have only this one connection.

I know there are a few switched empty spots in the fuse spot inside the vehicle (by your left knee) but wasn't sure if they would be enough for my application.

The other question is location of the relay. Which is better, closer to the battery source, the accessory being powered or the switched 12 volt source?

Thanks for the help. I think I had a wee too much wine with dinner and for some reason I'm having trouble accessing my RAM.

[slomatt]

Mike,

Pin 86 is only going to draw enough current to energize the coil in the relay, which is not a large load. It's fine to get +12v for pin 86 from the fuse box under the dash. Also, the coil has no polarity so technically you can put +12v on either pin 85 or 86 and ground the other side and it will still work fine.

Pins 30 and 87 are the NO (normally open) switch controlled by the coil.

The distance between the relay and the battery makes no difference, you just want to make sure your fuse is as close to the battery as possible.

http://www.rowand.net/Shop/Tech/images/RelayWiringGuide.jpg

- Matt

[4x4mike]

Thanks. My wine has worn off and now remember the reason for the relay and only needing enough juice to trip the coil. Your explanation just cemented it for me.

[L33T35T Tacoma]

Very nice Matt. Great explanation! :clap:

[4x4mike]

Question about the high side. The new lights that I wired are 55 watt and on my old truck I was running 100 watt bulbs in the same light with the stock harness. I wired these lights with 12 gage stranded wire on the high side. Will this be enough to handle the 100 watt bulbs or do I have to beef up the circuit somewhere else? FWIW I never had a problem with the other truck and stock harness that was 16g or lighter.

[CJM]

Should be fine Mike.

FWIW I wire things like this (and never have had an issue EVER). Power > fuse of appropriate size > high rated switch > out from switch to device. I usually use 14ga or 12 ga wiring.

Never an issue at all, I dont use relays-which is fine IF you use a properly rated switch.