how to trigger a relay 12v
Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=55521
Printed Date: July 07, 2025 at 1:43 PM
Topic: how to trigger a relay 12v
Posted By: LOBITO_SS
Subject: how to trigger a relay 12v
Date Posted: May 11, 2005 at 4:58 AM
New guy here and already I have a question :) Well here it goes. I'm putting together my 86 MC ss and I'm installing E-fans. The fan control that I got is ratted at 25 amps, and the fans are ratted at 35 amps. The control has a duel speed feature but so do the fans(two wire setup, 1-wire powered=low, 2 wires powered=high speed). I can run the fans of the control at low speed but not high. I was thinking of just installing a relay between the fans and control, but than I loose the dual speed feature. How can I set up a relay to click on just when it get a full 12 volts from the control? I think I just lost my self here with this :errr:
Replies:
Posted By: Captanham
Date Posted: May 11, 2005 at 8:22 PM
hook the high setting to pin 85, ground to pin 86, + 12v (fused of course) to pin 87a, the output from the low speed to pin 87, and the conection to the fan + goes to 30,, this would let your controll unit send the power to the fan at low speed, but then switches it over to a 12 volt sorce for the high speed ------------- Bad Boys Customs
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Posted By: Captanham
Date Posted: May 11, 2005 at 8:25 PM
OOPPSS, nevermind, you said the fan has dual inputs,, that setup only works if it has one,,,, instead, just run the low from the controll, straight to the low on the fan,, then run the same setup as up there,,, just dont' connect the low to the 87a ------------- Bad Boys Customs
audio - video - security
If you use it. Suport it. Donate to the 12 volt!
Posted By: LOBITO_SS
Date Posted: May 11, 2005 at 11:32 PM
Forgot to mention one thing. The fan control only has one wire to feed high and low power to the fans.
Posted By: soundman65
Date Posted: May 28, 2005 at 12:29 AM
I just installed a fan setup pretty much like yours, in a friend's 240sx. heres how it went: I have a thermostat switch hooked up monitoring the radiator temperature. when it gets too hot, the switch closes and sends +12V to engage the low speed relay. You can set that up either with a constant on 12V (fan keeps running for a few seconds after engine stops), or ignition-only 12V (fan stops no matter what when you turn the car off).
Then I ran a separate +12V line from inside the car through an on/off switch, to power the relay for the high speed. the way his works, only the high speed wire has to have power for it to run on high. you're saying yours needs power to both to run on high speed?
if you like that setup, let me know and I can sketch up a nice diagram for you.
Posted By: soundman65
Date Posted: May 28, 2005 at 12:31 AM
EDIT: I re-read your post and noticed the part about the fan control as opposed to thermostat switch. Not exactly sure how those work, did it come with a diagram?
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