# What is the yellow wire for in car stereo installations? **URL:** \ **Category:** Factual Questions\ **Created:** [April 26, 2006, 7:43am UTC](https://boards.straightdope.com/t/what-is-the-yellow-wire-for-in-car-stereo-installations/354266 "2006-04-26T07:43:11Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![AnabolicDoberman](https://avatars.discourse-cdn.com/v4/letter/a/ecd19e/32.png) [@AnabolicDoberman](https://boards.straightdope.com/u/AnabolicDoberman)\ **Post date:** [April 26, 2006, 7:43am UTC](https://boards.straightdope.com/t/what-is-the-yellow-wire-for-in-car-stereo-installations/354266/1 "2006-04-26T07:43:11Z")
Ok I know red is positive and black is negative.But what exactly does the yellow wire do? Some auto accessories only have red and black wires…and at some point I figured out to get it to work to just twist the yellow and red wires together and it worked. ---
**Author:** ![Lazlo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lazlo/32/9678_2.png) [@Lazlo](https://boards.straightdope.com/u/Lazlo)\ **Post date:** [April 26, 2006, 8:01am UTC](https://boards.straightdope.com/t/what-is-the-yellow-wire-for-in-car-stereo-installations/354266/2 "2006-04-26T08:01:41Z")
> [@AnabolicDoberman](#): > > Ok I know red is positive and black is negative.But what exactly does the yellow wire do? Some auto accessories only have red and black wires…and at some point I figured out to get it to work to just twist the yellow and red wires together and it worked. I can’t remember the convention offhand, but usually one (either red or yellow) is to be connected to the battery so that it’s always energized. The other is to be connected to the ACC wire, so that it is only energized while the key is turned. ---
**Author:** ![Fridgemagnet](https://avatars.discourse-cdn.com/v4/letter/f/22d042/32.png) [@Fridgemagnet](https://boards.straightdope.com/u/Fridgemagnet)\ **Post date:** [April 26, 2006, 10:52am UTC](https://boards.straightdope.com/t/what-is-the-yellow-wire-for-in-car-stereo-installations/354266/3 "2006-04-26T10:52:01Z")
There’s sometimes an output to an electric aerial too. There should be some sort of indication of the wiring on the unit, sometimes on a label, sometimes moulded into a plastic panel on the back. ---
**Author:** ![Nametag](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nametag/32/406_2.png) [@Nametag](https://boards.straightdope.com/u/Nametag)\ **Post date:** [April 26, 2006, 3:02pm UTC](https://boards.straightdope.com/t/what-is-the-yellow-wire-for-in-car-stereo-installations/354266/4 "2006-04-26T15:02:20Z")
> [@Lazlo](#): > > I can’t remember the convention offhand, but usually one (either red or yellow) is to be connected to the battery so that it’s always energized. The other is to be connected to the ACC wire, so that it is only energized while the key is turned. I just happen to have a radio harness adapter in my office today, and the guide says that the black wire goes to ground on the chassis, the red wire goes to the ignition switch, and the yellow wire goes directly to the battery to power the clock and other constant-draw features. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [April 26, 2006, 3:07pm UTC](https://boards.straightdope.com/t/what-is-the-yellow-wire-for-in-car-stereo-installations/354266/5 "2006-04-26T15:07:25Z")
> [@Nametag](#): > > I just happen to have a radio harness adapter in my office today, and the guide says that the black wire goes to ground on the chassis, the red wire goes to the ignition switch, and the yellow wire goes directly to the battery to power the clock and other constant-draw features. Yep. And if you twist them together and connect it to a switched source (ignition/accessory), the clock and station-preset memory reset each time the car is turned off. Connect them to an unswitched source (battery) and the unit won’t shut off when the car itself is shut off. ---
**Author:** ![Anachronism](https://avatars.discourse-cdn.com/v4/letter/a/e56c9b/32.png) [@Anachronism](https://boards.straightdope.com/u/Anachronism)\ **Post date:** [April 27, 2006, 10:04am UTC](https://boards.straightdope.com/t/what-is-the-yellow-wire-for-in-car-stereo-installations/354266/6 "2006-04-27T10:04:36Z")
> [@Fridgemagnet](#): > > There’s sometimes an output to an electric aerial too. There should be some sort of indication of the wiring on the unit, sometimes on a label, sometimes moulded into a plastic panel on the back. The Power antena lead is usually blue, also known as the amp turn on lead. Some stereos have a separate amp turn on and power antenna leads and lower the antenna (cut power to power antenna lead) when you listen to CDs. Not all stereos have a wire chart on them but it would be nice if they did. ---
**Author:** ![thirdname](https://avatars.discourse-cdn.com/v4/letter/t/d07c76/32.png) [@thirdname](https://boards.straightdope.com/u/thirdname)\ **Post date:** [April 27, 2006, 11:21am UTC](https://boards.straightdope.com/t/what-is-the-yellow-wire-for-in-car-stereo-installations/354266/7 "2006-04-27T11:21:34Z")
Don’t cut the yellow wire!!!