Relay for Ignition bypass

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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=9007
Printed Date: August 28, 2025 at 5:23 AM

Topic: Relay for Ignition bypass

Posted By: brylande
Subject: Relay for Ignition bypass
Date Posted: February 03, 2003 at 1:55 PM

I've just put in a ignition bypass setup in my pickup so that I can let it run without the keys while I'm in getting coffee or for other quick trips like that. I would like to have it kill the motor though if the brake pedal is touched. That's where I need help! I have a relay with 30 hooked to 12V constant; 87 hooked to ignition wire; 86 to one side of the switch and the other side of the switch spliced into that same ignition wire; and 85 to the brake wire that shows 12V when the brake is pressed. The bypass works fine except for the brake part. It doesn't kill the motor. What am I missing? I've hooked to the other brake wire, but the brake pedal has to be pressed to make the system work so a guy would figure that the other wire would be the one I'd want; however it isn't! I don't know that much about relays, but just enough to get in trouble so any help would be great. Thanks

Replies:

Posted By: GMC4x4Guy
Date Posted: February 03, 2003 at 2:52 PM

First, make sure that the switch isn't momentary. Then make it connect between the 12V constant wire on your #30 terminal. Here's how the rest of the connections go:

#85--to 12V when the brake is pressed (leave it where you have it)

#87A--to the ignition wire (not a typo, move the wire to #87A)

#86--to ground

The relay doesn't switch the current of the ignition so make sure you have a switch that can handle the current. It would be best to add another relay to handle the current intstead of the switch. Also, everytime you press the brake the relay will activate so you might hear it. This relay setup just kills the engine; after the brake is pressed it switches the ignition power off. When the brake is released the ignition will turn back on but the engine would need to be re-started and of couse there's no key. If you want to use two relays just let me know and I'll post how to wire it.

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"Drive it like you stole it"

Posted By: jrilla
Date Posted: February 24, 2003 at 4:04 PM

I know this post is old, but I saw it and thought it was a pretty slick idea for anyone who didnt want RS installed. I drew this up real quick like and thought I would post it. You have to copy and paste the link in a new window.

https://12voltinstallations.8m.com/index.html

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J Rilla

Owner/Installer