# How would I add a relay to turn on a new device when the car is on?

**URL:** <https://forums.speedlife.net/t/how-would-i-add-a-relay-to-turn-on-a-new-device-when-the-car-is-on/27716>\
**Category:** NYSpeed Automotive\
**Created:** [April 16, 2007, 11:57am UTC](https://forums.speedlife.net/t/how-would-i-add-a-relay-to-turn-on-a-new-device-when-the-car-is-on/27716 "2007-04-16T11:57:32Z")\
**Posts on this page:** 1\
**Showing post:** 15

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**Author:** ![JustinH](https://avatars.discourse-cdn.com/v4/letter/j/9fc29f/32.png) [@JustinH](https://forums.speedlife.net/u/JustinH)\
**Post date:** [April 24, 2007, 7:45am UTC](https://forums.speedlife.net/t/how-would-i-add-a-relay-to-turn-on-a-new-device-when-the-car-is-on/27716/15 "2007-04-24T07:45:22Z")

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yep, a four dollar harbor freight voltmeter works great for figuring out what is what when you have a ghetto hacked stereo harness.

I went through this with my jetta.

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