how to make led go off when engine starts

Printed From: the12volt.com
Forum Name: Lights, Neon, LEDs, HIDs
Forum Discription: Under Car Lighting, Strobe Lights, Fog Lights, Headlights, HIDs, DRL, Tail Lights, Brake Lights, Dashboard Lights, WigWag, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=85696
Printed Date: May 12, 2025 at 9:39 AM

Topic: how to make led go off when engine starts

Posted By: 3square
Subject: how to make led go off when engine starts
Date Posted: November 15, 2006 at 10:16 PM

basicly i want to make a fake alarm status light

so the led would go on when i turn off the engine, and would turn off when i start the engine.

i set it up before but forgot which fuse i tapped into.

Replies:

Posted By: KPierson
Date Posted: November 16, 2006 at 5:21 PM

Hook the + side of the LED up to the main 12vdc wire in the car. Hook the (-) side up to the main ignition wire in the car. Make sure you are using a flashing 12vdc LED or it won't work (for very long).

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Kevin Pierson

Posted By: 3square
Date Posted: November 17, 2006 at 4:04 AM

thanks for the reply.

i'm using a running led bar about 8 leds

it should be fine?

Posted By: master5
Date Posted: November 17, 2006 at 11:14 AM

Yes it should be fine. If the running bar you are using has 3 wires the 3rd is to turn it on during a negative signal.

What you will do is connect red to 12v positive, black to ground, and the 3rd wire to ignition. What happens is (like the above post) is when the ignition if off the wire will send a neg. to the led bar and it will operate, when the key is on that wire turns 12v+ and the led's turn off. No prob.

If only a 2 wire (flashing) unit designed for 12v it will wire as KPierson above posted.

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