I'm a car install n00b: How do I hardwire a 12v device to car's electrical system?

[UNCjigga]

I have a 2002 Honda Accord EX. Haven't found any useful diagrams or pictures on splicing into a 12v wire somewhere in car's electrical system, and how to run the wire up to the top of the dashboard without having wires hanging all over the place.

Tried http://www.the12volt.com/ but it wasn't much help. Any help appreciated!

 

[Fiveohhh]

if theres not much load on the wire, 3m i think makes some things you just crimp over your old wire w/ 12v in and crimp your wire in it too, and you have a hot 12v line, just make sure to fuse the wire. as far as running the wire I nrmally just pull the a pillar off and run it behind the dash up the pillar and above the headliner.

 

[Mark R]

Have a look behind the radio - and splice into there. I've never tried a honda, but on every other car I've worked on there are 2 power feeds - one's always on, and one comes on with the ignition.

If you only need a small load this will be fine. You should splice in using some insulated crimp connectors - and ideally should cover these with heatshrink sleeving, though electrical tape would probably do.

Routing the wire really depends on the car - but if you're behind the dash to get at the stereo wires anyway, then there shouldn't be too much difficulty getting the wire down the back. On some cars though, you may have to take the whole dash out - i've seen that done before.

 

[kami333]

The splices are called T-taps and you can get them at many places including Walmart, RadioShack and Home Depot.

 

[UNCjigga]

Ok, but someone else suggested getting into the ignition harness (???) and splicing into a 12v lead there, and then running the wire up behind the dash. Trouble is, I looked down there and couldn't figure out where to run the wire. I think I might just get my dad to help on this one.

BTW, the device is a PDA holder/charger with a speaker and an accessory power outlet for a GPS receiver (which I will be using to power my belkin GPS.) Don't know what kind of load this will put on anything.

 

[The Stigenator]

before you mess with any electrical..

disconnect battery before working.. you dont want the airbag going off because of it. Disconnect battery, wait 90 seconds and then start working on it.

For your device, you can pinch it off the radio's 12V constant or switched power supply.

 

[kami333]

Personally that's too much work for me, why go into the ignition harness when the radio or cigarette lighter wires are clearly labeled.

 

[Pepsi90919]

how about just running a new wire with an inline fuse.

 

[UNCjigga]

Originally posted by: Pepsi90919
how about just running a new wire with an inline fuse.

Huh? ...n00b here, but I think you mean running a new line direct to the source of juice (the battery)...is that what you are talking about? I have no idea how that works, and how'd I'd regulate to 12v etc.

 

[kt]

Originally posted by: Jigga

Originally posted by: Pepsi90919
how about just running a new wire with an inline fuse.

Huh? ...n00b here, but I think you mean running a new line direct to the source of juice (the battery)...is that what you are talking about? I have no idea how that works, and how'd I'd regulate to 12v etc.

Most car batteries now a day are 12V.

 

[mAdD INDIAN]

Originally posted by: Jigga

Originally posted by: Pepsi90919
how about just running a new wire with an inline fuse.

Huh? ...n00b here, but I think you mean running a new line direct to the source of juice (the battery)...is that what you are talking about? I have no idea how that works, and how'd I'd regulate to 12v etc.

The easiest way would to be to tap the wire that goes to the cigarete lighter.

 

[kami333]

Originally posted by: Pepsi90919
how about just running a new wire with an inline fuse.

Problem with that is that it would be always live, unless you put a relay on it (which I don't think the OP is up to) and you'd more than likely end up draining the battery.

 

[Antisocial Virge]

Originally posted by: kami333

Originally posted by: Pepsi90919
how about just running a new wire with an inline fuse.

Problem with that is that it would be always live, unless you put a relay on it (which I don't think the OP is up to) and you'd more than likely end up draining the battery.

Are you thinking of a switch instead of a relay? A relay would not be needed to stop current flow. I know on all the older cars I worked on, the lighter had constant power even without the key being on.
EDIT: Yes I agree that the lighter or radio would be a perfect spot. From things you have said it might be best if you got some help with it.

 

[0roo0roo]

cig lighter?

 

[kami333]

Originally posted by: Antisocial-Virge

Originally posted by: kami333

Originally posted by: Pepsi90919
how about just running a new wire with an inline fuse.

Problem with that is that it would be always live, unless you put a relay on it (which I don't think the OP is up to) and you'd more than likely end up draining the battery.

Are you thinking of a switch instead of a relay? A relay would not be needed to stop current flow. I know on all the older cars I worked on, the lighter had constant power even without the key being on.
EDIT: Yes I agree that the lighter or radio would be a perfect spot. From things you have said it might be best if you got some help with it.

I like relays because it's automatic so you never forget to turn it off, I have a 400W inverter hardwired into my car with the relay connecting to the cig lighter wires since mine are ignition switched, though I also have a switch on it to bypass the relay (lots of redundancy). In my experience imports tend to have the cig lighters ignition switched, I know that Honda, Nissan and Subaru have a tendency to do it that way (not sure if it is true for all their cars), but it's best to find out what the car does.

 

[Squisher]

Originally posted by: 0roo0roo
cig lighter?

That's what I usually use, or an unused prong on the fuse box array.

cig lighter pulls some serious amps.

 

[Antisocial Virge]

Originally posted by: kami333

Originally posted by: Antisocial-Virge

Originally posted by: kami333

Originally posted by: Pepsi90919
how about just running a new wire with an inline fuse.

Problem with that is that it would be always live, unless you put a relay on it (which I don't think the OP is up to) and you'd more than likely end up draining the battery.

Are you thinking of a switch instead of a relay? A relay would not be needed to stop current flow. I know on all the older cars I worked on, the lighter had constant power even without the key being on.
EDIT: Yes I agree that the lighter or radio would be a perfect spot. From things you have said it might be best if you got some help with it.

I like relays because it's automatic so you never forget to turn it off, I have a 400W inverter hardwired into my car with the relay connecting to the cig lighter wires since mine are ignition switched, though I also have a switch on it to bypass the relay (lots of redundancy). In my experience imports tend to have the cig lighters ignition switched, I know that Honda, Nissan and Subaru have a tendency to do it that way (not sure if it is true for all their cars), but it's best to find out what the car does.

But he would need a signal wire to kick the relay letting the voltage make it from the battery, there is no need for that since the signal voltage wire in this situation would have enough voltage to run what he wants I would imagine. For an inverter, like in your situation, a relay would work well since the amp draw is significantly higher. Same as large car stereo amps with the signal wire setup they use.

 

[Analog]

you can use a simple parallel splice on a 12V wire from an accessory under the dash. How do you find a good one? Well, first of all, decide whether your device requires to be on when your ignition is on. If it is, then you need a volt meter to probe various hot leads based on the first question (with the negative lead touching a shiny bolt or chassis part). You can safely poke through the insulation on wires you can't find the ends to without worry.

When you find a good one, then splice away. Someone already said using an in-line fuse may be a good idea, you can get these at Radio Shack. This may be important, because if the device you're powering shorts out, then it will take the fuse out (as long as its rated lower than the fuse that supplies the wire you spliced to), and prevents the device that you tapped from from going offline.

HTH

 

[UNCjigga]

LOL, I've put this project on hold until I find a professional to help me!

I found wiring diagrams for the ignition harness and radio harness, but I haven't for the life of me figured out how to get access to these wires without tearing my car apart (its a lease vehicle!) I'm not good at figuring out how to take out the console/dash plastics. I found two screws under the radio that appeared to be holding the 'dark' part of the console in place, but when I removed them and tried to pull the panel up, the clock and a/c vents came up too, and the connecting hoses and stuff seemed to be holding the panel back so I couldn't remove it completely to get to the radio.