# Ignition switch 12V wiriging (which is the 12V?) **URL:** \ **Category:** SON240sx Automotive\ **Created:** [October 7, 2003, 1:08pm UTC](https://forums.speedlife.net/t/ignition-switch-12v-wiriging-which-is-the-12v/80141 "2003-10-07T13:08:46Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Gonad](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/gonad/32/5481_2.png) [@Gonad](https://forums.speedlife.net/u/Gonad)\ **Post date:** [October 7, 2003, 1:08pm UTC](https://forums.speedlife.net/t/ignition-switch-12v-wiriging-which-is-the-12v/80141/1 "2003-10-07T13:08:46Z")
Ok, trying to hook up the 12V power wire for my Autometer tach and I’m not sure which wire to tap into. Looking in the FSM (as cryptic as it is), the IGNITION SWITCH harness (E108), there are 5 wires coming out of it: - WHITE - BLACK / WHITE - BLACK / RED - BLACK / YELLOW - BLUE There is also two wires going to the IGNTION KEY: - RED - RED / WHITE Can someone tell me which wires to tap into so the tach is only on when ignition is on? ---
**Author:** ![Sasha\_SG](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/sasha_sg/32/5477_2.png) [@Sasha\_SG](https://forums.speedlife.net/u/Sasha_SG)\ **Post date:** [October 7, 2003, 2:13pm UTC](https://forums.speedlife.net/t/ignition-switch-12v-wiriging-which-is-the-12v/80141/2 "2003-10-07T14:13:07Z")
just hook it up to ur stereo, or any wire that only gets power when the car is on does (fuel pump) ---
**Author:** ![Gonad](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/gonad/32/5481_2.png) [@Gonad](https://forums.speedlife.net/u/Gonad)\ **Post date:** [October 7, 2003, 2:19pm UTC](https://forums.speedlife.net/t/ignition-switch-12v-wiriging-which-is-the-12v/80141/3 "2003-10-07T14:19:59Z")
Yea, guess I’ll do that. So I hook it up to the IGNITION wire on the stereo right? Or the BATTERY wire? ---
**Author:** ![iQuAGoD](https://avatars.discourse-cdn.com/v4/letter/i/f05b48/32.png) [@iQuAGoD](https://forums.speedlife.net/u/iQuAGoD)\ **Post date:** [October 7, 2003, 6:16pm UTC](https://forums.speedlife.net/t/ignition-switch-12v-wiriging-which-is-the-12v/80141/4 "2003-10-07T18:16:01Z")
you need to hook up to the 12v switched, not 12v constant… so that would be ignition ---
**Author:** ![Gonad](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/gonad/32/5481_2.png) [@Gonad](https://forums.speedlife.net/u/Gonad)\ **Post date:** [October 7, 2003, 6:56pm UTC](https://forums.speedlife.net/t/ignition-switch-12v-wiriging-which-is-the-12v/80141/5 "2003-10-07T18:56:03Z")
Well almost ran into some trouble doing this. I didn’t bother to disconnect negative battery cable before splicing my wires and as I was pulling my stereo I noticed my legroom light went off. Then I noticed the clock, chimes, dome light and map lights didn’t work. Turned car on and as soon as I turned it on the wiper went once. Heh…strange shit. Turned out I blew my ROOM LIGHT fuse. Replaced it and it works fine. And yea I spliced it with the ignition +12V so it’s working fine. I’ll post pics of my ghetto tach setup tomorrow 🙂 ---
**Author:** ![Sven](https://avatars.discourse-cdn.com/v4/letter/s/e47c2d/32.png) [@Sven](https://forums.speedlife.net/u/Sven)\ **Post date:** [October 7, 2003, 8:08pm UTC](https://forums.speedlife.net/t/ignition-switch-12v-wiriging-which-is-the-12v/80141/6 "2003-10-07T20:08:58Z")
Something to consider: If you are running a lot of devices on switched +12V power (like me) you might do well do run a smaller guage wire into the passanger comparment and use a relay to switch it (switched by cig. lighter). This way you don’t have to worry about overloading that circut (and you can install inline fuses of course to ensure you don’t start any fires) ---
**Author:** ![Racer\_XTREME](https://avatars.discourse-cdn.com/v4/letter/r/e47c2d/32.png) [@Racer\_XTREME](https://forums.speedlife.net/u/Racer_XTREME)\ **Post date:** [October 7, 2003, 8:37pm UTC](https://forums.speedlife.net/t/ignition-switch-12v-wiriging-which-is-the-12v/80141/7 "2003-10-07T20:37:44Z")
> [@Gonad](#): > > Well almost ran into some trouble doing this. I didn’t bother to disconnect > negative battery cable before splicing my wires and as I was pulling my > stereo I noticed my legroom light went off. Then I noticed the clock, > chimes, dome light and map lights didn’t work. Turned car on and as > soon as I turned it on the wiper went once. Heh…strange s\*\*t. > > Turned out I blew my ROOM LIGHT fuse. Replaced it and it works fine. > > And yea I spliced it with the ignition +12V so it’s working fine. I’ll post > pics of my ghetto tach setup tomorrow 🙂 which colour was the igntion wire? ---
**Author:** ![Gonad](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/gonad/32/5481_2.png) [@Gonad](https://forums.speedlife.net/u/Gonad)\ **Post date:** [October 7, 2003, 9:11pm UTC](https://forums.speedlife.net/t/ignition-switch-12v-wiriging-which-is-the-12v/80141/8 "2003-10-07T21:11:45Z")
From the stereo? The red one. Well I spliced it on the harness coming out of my stereo so the head-unit manual had the colour codes.