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Old 08-13-2012, 04:23 PM   #1
THE "10" SILVERADO
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Relay Question?

I'm putting an ignition kill switch in my truck (along with another switch on the NSS) but I've got a question about which relay to use.

For the ignition I don't want to use a Bosch style because if the switch accidentally turns off while I'm driving it will still kill the coil power, what kind of relay can I put in that would cut power when the switch is off but after the car is started (ignition on) would stay on even if the switch turns off? So say if I hit a bump and the switch malfunctions it would stay running and only turn off when I killed the engine (killing the engine would work like a reset button or something). I'm sure there is something like that out there but I don't know what it would be called to get it.

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Michael
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Old 08-13-2012, 05:46 PM   #2
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Re: Relay Question?

Try here http://www.the12volt.com/relays/page2.asp
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Old 08-13-2012, 10:37 PM   #3
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Re: Relay Question?

Thanks for the reply but that confused me a little....read through it but that's some pretty advanced stuff there.
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Old 08-13-2012, 11:45 PM   #4
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Re: Relay Question?

The purpose of a relay is to allow a higher voltage or load to be switched and controlled by a low voltage low draw circuit. This protects switching components such as the headlight switch, electric fans, electric fuel pumps switches, etc. The ignition switch is designed to carry the low amperage draw of the ignition coil so why do you want to put a relay there. If you want to keep the engine running if the switch cuts off you could just put a hidden toggle switch in the coil feed wire and feed it from any hot source off the fuse panel, doing away with the ignition switch altogether as the ignition source.

Having more than the normal voltage to the coil may be necessary if the engine is to be revved more than 6000 RPMs as in drag racing or if you are feeding more than the normal amount of circuits off the ignition switch.
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Old 08-13-2012, 11:53 PM   #5
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Re: Relay Question?

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Originally Posted by VetteVet View Post
The purpose of a relay is to allow a higher voltage or load to be switched and controlled by a low voltage low draw circuit. This protects switching components such as the headlight switch, electric fans, electric fuel pumps switches, etc. The ignition switch is designed to carry the low amperage draw of the ignition coil so why do you want to put a relay there. If you want to keep the engine running if the switch cuts off you could just put a hidden toggle switch in the coil feed wire and feed it from any hot source off the fuse panel, doing away with the ignition switch altogether as the ignition source.

Having more than the normal voltage to the coil may be necessary if the engine is to be revved more than 6000 RPMs as in drag racing or if you are feeding more than the normal amount of circuits off the ignition switch.
I want to cut the coil power feed with a toggle (for security when I'm away from the truck) but I want to put something like a latching relay in the feed to keep the power to the coil in case the toggle accidentally turns off driving.

So once the ignition and toggle are on it gets power but if the toggle goes off (once it has power) it will continue to have power until the ignition is cut.
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Old 08-14-2012, 12:50 AM   #6
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Re: Relay Question?

If you want to latch the relay just jump terminal 87 to 86 that way the relay will energize itself regardless of the state of the kill switch and once the ignition is turned off the relay shuts down.
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Old 08-14-2012, 01:02 AM   #7
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Re: Relay Question?

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Originally Posted by fixit-p View Post
If you want to latch the relay just jump terminal 87 to 86 that way the relay will energize itself regardless of the state of the kill switch and once the ignition is turned off the relay shuts down.
Thanks man! I figured I would end up with 2 relays and a complicated setup but that seems simple enough. Guess I'll only end up spending $5 for the relay then.
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