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Home > Visual / Audio Mods > Interior Styling > How to wire multiple switches for lighting/accessories

How to wire multiple switches for lighting/accessories

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SoCalCory Castaic California, US Chief Mechanic	I want to wire up 3-4 switches in my 08 Tc. I want to wire from the battery into the car, and from there split the power between 3 or 4 switches. What size wire would be best? Should i use an inline fuse? and what size (interior and underglow lighting) fuse? Also where does the wire go through the firewall? Thanks, Cory
[#] Apr 26, 2008 04:24pm
07TouringCoupe Baltimore Maryland, US Scion Guru	For this the best wire prolly is 16 awg. You should need more than that, its only 12 volts going through it. Now keep in mind if you bring the feed from the battery, the first switch you take that to is gonna have a constent 12 volts to all the time. Meaning you are going to be able to arm this switch with no key in the ignition or anything. Thats just a heads up so you dont hit the switch and leave it on, and it possibly kill the battery. A car is only as good as it's driver.
[#] Apr 27, 2008 09:41am
SoCalCory Castaic California, US Chief Mechanic	Ok, thanks, I was also thinking of using the piggyback fuse with the wire already attached and run that to the switches. I want to run both underglow and interior lighting so far, but i might go bigger in the future so i want the fuse to be able to handle a lot. What size fuse should i use? And this idea just dawned on me :-/ I hope it works.
[#] Apr 27, 2008 07:15pm
07TouringCoupe Baltimore Maryland, US Scion Guru	Yea i know what you mean. I had the same problem when hooking up my nitrous kit and all the accessories. Seeing that its just under glow and intreior. To play iot safe i'd say a 15 amp fuse should be fine A car is only as good as it's driver.
[#] Apr 28, 2008 06:08pm
SoCalCory Castaic California, US Chief Mechanic	K thanks, Can I wire that on the inside fuse box? That fuse box seems a little small??
[#] Apr 28, 2008 06:09pm
07TouringCoupe Baltimore Maryland, US Scion Guru	This maybe ghetto or whatever, but i pulled the fuse i needed out, and stripped the wire back and wrapped the wire around the fuse and shoved it back in to its correct slot. Never had a problem since A car is only as good as it's driver.
[#] Apr 28, 2008 06:18pm
07sctc South Carolina, US Chief Mechanic	^^you can do that, but you run the chance of defroming the connector in that side of the fuse box. the best way to do this is to use a relay per switch. most switches aren't rated for much current at all and will endup melting the internals of the switch from too much heat produced in the switch. if you wanna do it the right way.... get a automotive relay from whereever pin 85 will go to 12v (fused) pin 86 will go to one side of the switch, the other side of the switch will go to ground pin 30 will go to a high current 12v source ie. battery or igintion harness (this also needs to be fused, but use a fuse that is equal to or less than the relays amp rating) pin 87 will go to whatever you are powering. when the switch is flipped this will cause whatever voltage is on pin 30 to be connected to the load on pin 87. i usually use the igition harness wires because it save time by not having to run wire under the hood. JUST REMENBER TO FUSE ALL CONNECTIONS TO KEEP FROM BURNING YOUR CAR DOWN. i have had to rewire some cars in the past because of people not doing it right in the first place and ending up burning the carpet and stuff from a shorted wire that hadn't been fuse (ie. power wire to an amp that wasn't fused at the battery = burnt up car.) beware of the mad sciontist ! ask me your car audio and electronics questions!!
[#] Apr 28, 2008 09:41pm
SoCalCory Castaic California, US Chief Mechanic	Thanks for the help, but i am a visual learner and if u had pics i would so appreciate it. Thanks for your replys. Cory
[#] Apr 28, 2008 11:23pm
07sctc South Carolina, US Chief Mechanic	here is a rough schematic of what i was talking about if it helps beware of the mad sciontist ! ask me your car audio and electronics questions!!
[#] Apr 29, 2008 12:15am
07sctc South Carolina, US Chief Mechanic	beware of the mad sciontist ! ask me your car audio and electronics questions!!
[#] Apr 29, 2008 12:16am
SoCalCory Castaic California, US Chief Mechanic	It does, thanks, Could you do one more thing? just label it a little better for me... it is so much appreciated. Like for in stance if the top 12 V is the batery could u just label battery? also could you suggest what size wire and size fuse? Thanks, so much Cory
[#] Apr 29, 2008 12:29am
07sctc South Carolina, US Chief Mechanic	the size wire and relay will depend on what you are running the power to. here is a table from the12volt.com on cable size vs. current draw. there is a better one that takes into account the length of the wire, but for short length less then 10 or so ft. these numbers should be close enough. the coil wires (pins 85 and 86) can be fairly small around 16 to 20 gauge since they aren't carrying much current at all. the wire that you connect to the battery (pin 87) and to your component (pin 30) can be determined by the chart below, but since most automotive relays are rated at 30 amps max., then 14 gauge should be sufficient. Power & Ground Cable Specs gauge vs. current capacity 10 gauge 60 amps 12 gauge 40 amps 14 gauge 25 amps 16 gauge 15 amps i will try to get you a new image when photobucket is back up; but to clear things up on the schematic, both the +12v can be the battery or you can tap into the +12v wire in your ignition harness under the dash to keep from running to many wires under the hood. if you don't know how to use a volt meter to find the constant +12 volt wire in the ignition harness under the dash then i would just run it to the battery. either way will work. just remember to fuse the wire within 1 ft. of the battery or whereever you get the power from. as far as fuse sizes a 25 or 30 amp will be fine to use between the battery and pin 87. a 5 amp fuse would be fine to use between your battery and pin 87. by the way you can connect pin 85 to pin 87 on the relay with a short piece of wire and the 5 amp fuse to keep from having two wires to run to the battery. i will make a new schematic for you when photobucket is back up. hope this helps, i know its a bit wordy. beware of the mad sciontist ! ask me your car audio and electronics questions!!
[#] Apr 29, 2008 02:51am
07sctc South Carolina, US Chief Mechanic	i added the new schematic to my profile pics since photobucket is down. i also changed a few things on it to better suit your needs. i swapped pins 87 and 30 from the first schematic so now 87 will go to the battery and 30 to whatever you are powering. this keeps the normally closed pin 87a without any voltage on it while the toggle switch is open otherwise it would be "hot" when the switch is off. i hope none of this is to confusing. good luck, let me know if you need anything. beware of the mad sciontist ! ask me your car audio and electronics questions!!
[#] Apr 29, 2008 03:21am
SoCalCory Castaic California, US Chief Mechanic	Thanks so much for the help, I see the switch in your schematic but what exactly is the relay?... If i splice into the ignition wire then my switch and components will only work if the ignition is on correct? I see the switch however, it says that the component power is coming off of the relay? Thanks, and sorry, this is my first electrical mod. Cory
[#] Apr 29, 2008 10:12am
FrAnkRYzzO Perry Hall Maryland, US $upervillain for Hire	Fixed the pic. Props on the instructions! ............... Search or one of these adorable kittens WILL DIE!
[#] Apr 29, 2008 10:19am
07sctc South Carolina, US Chief Mechanic	here is the new schematic, use this one. here is a little theory on relays a relay is an electromagnetic switch that allow you to power something that needs more current than the circuit you are interfacing with. the relay has 5 connections (pins). 85 and 86 these are the "coil" pins 87a normally closed 87 normally open 30 common the basic way it works is that when there is 12 volts across the "coil" (pins 85 and 86) then the connection between pins 87 and 30 is made. when energized (12 volts across pins 85 and 86) the electromagnet inside the relay causes pins 87 and 30 to become connected. when the electromagnet is de-energized (0 volts across pins 85 and 86) pins 87a and 30 are connected. so basically what you are doing is that when (refer to the new schematic) you flip the switch you are causing the "coil" in the relay to be energized since you have 12 volts on pin 85 (from the battery) and Ground on pin 86 (through the switch). this makes the connection between 87 and 30 so that whatever is connected to pin 87 is now going through the relay to 30. the switch you install will have one side connected to 86 on the relay and the other to bare metal in the car. the bare metal will give you the ground connection. Ground is just a term meaning a voltage reference point, which on a car is the chassis. since the negative on the battery is connected to the chassis and your switch is connected to the chassis, this allows you to put 12volts across the coil of the relay when you close your switch. to answer your questions... Q. If i splice into the ignition wire then my switch and components will only work if the ignition is on correct? A. there are many many ways to wire a relay. the ignition harness has +12 volts constant (battery) and two ignition wires which are only energized when the car is on. these are heavier gauge wires probably 12 gauge that you can find by tracing them back from the key switch. if you want the component to be used when the ignition is off the pin 87 would be connected to a constant voltage source (battery or constant wire). if you didn't want that then use a "switched" voltage source (ignition wire) on pin 87. it really just depends on what you what it to do. 12V Constant - red or white (ignition harness) Ignition - blue (ignition harness) Second Ignition - yellow (ignition harness) I hope this helps clear things up. let me know if you have any other questions. beware of the mad sciontist ! ask me your car audio and electronics questions!!
[#] Apr 30, 2008 09:09am
FrAnkRYzzO Perry Hall Maryland, US $upervillain for Hire	Again, very nice write up! edited title for easier searching ............... Search or one of these adorable kittens WILL DIE!
[#] Apr 30, 2008 09:33am
07sctc South Carolina, US Chief Mechanic	thanks man i love electronics and helping people out with it! beware of the mad sciontist ! ask me your car audio and electronics questions!!
[#] Apr 30, 2008 09:38am
07sctc South Carolina, US Chief Mechanic	as we talked about in the pm component 1 can be your led strips, and component 3 can go to your underbody neons. component 2 could go to whatever else you wanted to power. as far as the underbody neons, most of those kits come with switches and a transformer and are meant to stand alone but you could still do it this way. you would just have to look at install guide to see how to interface with it. personally i would just use the stuff that comes with the underbody kit for it. you csn use this schematic for other stuff. any more questions let me know. i can email you the pic if it looks to blurry here. [url=null]http://i278.photobucket.c...01/nasutton/3switches.jpg[/url] beware of the mad sciontist ! ask me your car audio and electronics questions!!
[#] May 01, 2008 04:38pm
dougc84 Richmond Virginia, US Oil Changer	just a thought, try one of those add-a-fuse things from radio shack or any auto parts store. anywhere you have a fuse, you pop the thing in and it literally adds a second fuseholder with a line to your accessories. plus, you don't have to run direct off your battery, you don't need as much wire, and the fuses are just below where the oem switch plates are. and anything 18awg or thicker is fine. i'd run 16 or 14 just to be on the safe side. 20 or thinner may be fine for VERY short distances, but might blow up in your face. just go to radio shack and pick up a spool of 16awg speaker wire and you'll be fine. and if you're running interior LEDs (highly recommended over neons!!!), you will most likely never need more than a 10 amp fuse, unless you're just going nuts with lights.
[#] May 09, 2008 11:14pm
07sctc South Carolina, US Chief Mechanic	^^^that is the only way i would tap into the fuse box. the fuse taps can still cause a problem with the connection inside the fuse box. if you do this make sure you put the fuse tap on the output side of the fuse and not the supply side. if you put it on the supply side the you are just bypassing the fuse and could end up with that not so good burnt smell in the car. the schematic i posted earlier is just a generic layout that could be used for anything. running wire to the battery or somewhere else besides the fusebox is still the best way to go for the life of the fusebox. beware of the mad sciontist ! ask me your car audio and electronics questions!!
[#] May 10, 2008 09:26am
SoCalCory Castaic California, US Chief Mechanic	Thanks so much for the feedback. I mounted my internal lights and they look awesome. I followed 07sctc's amazing diagram. So once again thanks for the help and pic to come tonight i hope. Cory
[#] May 10, 2008 11:19am
ErnDawg El Paso Texas, US Vehicle Designer	somone should really do a walkthrough with lighting...i'm not gonna say who....
[#] May 10, 2008 12:49pm
dougc84 Richmond Virginia, US Oil Changer	i might be able to do one tomorrow afternoon. depends on if i have time.
[#] May 10, 2008 01:02pm
07sctc South Carolina, US Chief Mechanic	glad to hear the install went good...looking foward to pics!! beware of the mad sciontist ! ask me your car audio and electronics questions!!
[#] May 10, 2008 04:47pm

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