relay install

i currently have nice lighted rocker switch running my intercooler fan all is well there. but would like to incorporate my pusher fan in the circuit which would involve a relay of course. ive managed to over think the process and need help with the wiring.. what i currently have : {both fans grounded } , and {both fans positive wires together} and a {fused connection from 12v battery} and of course the { two wires from the switch} inside. which sets of wires go to which posts on relay ? 30-85-86-87-87a...
had it wired without relay and worked fine--- just dont feel safe like that..

12V --> Fuse (5A or so) --> Switch --> 85 or 86, the other one to ground. That controls the coil. Doesn't matter which terminal is which, just one is switched 12V, the other is ground. Or even, if you wish, use this:

12V --> Fuse (5A or so) --> 85 or 86 --> 86 or 85 --> Switch --> Ground

The second one puts the relay in the circuit so that a short on the control side will be fused and have the coil in the circuit, avoiding excessive current.

12V --> Fuse (Big honker - 50A or bigger) --> 87 --> 30 --> Fan --> Ground

That puts the 12V in on the NO contact (Normally Open), takes the COM (Common) to the fan, and the ground to ground.

I'd put each fan on its own relay, or use something like the Echlin 200A relay, to make sure you didn't overcurrent the contacts.

If you use multiple relays, just wire the 85 and 86 in parallel on both, and switch that part.

RwP

cool

thanks ralph that should help i tried different configurations with a relay i had lying aroung with no results probably a bad relay i hear stuff moving around inside,, the thing that throws me off the most is the lighted switch in place.. without that in the mix its pretty strait forward. but id rather control fans manually..so i want the switch.... i wont forget and leave it on.. i really need a diagram but cant find one exactly for my needs

How is the internal light wired with the switch?

I've seen where you had 12V in, ground for the light, and pass through for the device.

I've also seen 12V for the light, device being switched, and a common ground.

It'll make a small difference.

Ideally, the light is wired separate from the switch itself.

RwP

switch

yeah thats the ? been so long since i installed switch ive forgot.... i know switch had 3 poles and i had 2 wires returning under the hood one to batt one to positive fan wire and negative fan wire to chasis cant recall where i sent the third wire i may have to get back in there and verify just didnt want to go back in there again..

pretty sure i grounded switch inside maybe that was the third wire. at any rate switch is operational just need to know where to place the 2 wires from it in the mix

maybe this helps if not let me know and ill pull switch and verify connections

anlo said:

yeah thats the ? been so long since i installed switch ive forgot.... i know switch had 3 poles and i had 2 wires returning under the hood one to batt one to positive fan wire and negative fan wire to chasis cant recall where i sent the third wire i may have to get back in there and verify just didnt want to go back in there again..

pretty sure i grounded switch inside maybe that was the third wire. at any rate switch is operational just need to know where to place the 2 wires from it in the mix

maybe this helps if not let me know and ill pull switch and verify connections

Click to expand...

Easiest? Take the wires going to the fan now from the switch, wire it to 85 or 86, and take the other of 85 or 86 to ground.

Take fused +12V, wire to 87, run 30 to the fan.

Minimum changes that way.

RwP