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12V power source faq

PostPosted: Mon May 15, 2006 10:01 pm
by CMS-GT4
I am making this thread in hopes we can sticky some info about wiring for electrical noobs (myself) for future reference.

If we can pack more elecrical how to info in here I will chang the name of it. Not sure if anyone wants post a faq on the basics like sauder or anything. I have these down myself.

I was hoping we could produce a list of 12v power sources for adding addtional eqipment in the trunk, cabin, and under the hood of the car.

For example if someone needs to power something like water injection in the trunk or gauges in the cabin (along with piggy backs etc..) and under the hood maybe for water injection water pumps etc... Pictures wire info and color could be useful.

PostPosted: Tue May 16, 2006 4:46 pm
by Simba
Randomly hacking into vehicle power sources is a generally bad idea. If you want to wire something properly, you should make a distribution block off the battery and switch what leads you need via a relay hooked up to the ignition or accessory circuit.

Hardly anyone ever does this, of course, but that's the reason just about every AT owner hates the person who owned the car before them with a passion. :shoots:

I typically use a four-fuse block with two 20A feeds, one switched and one constant, and two 5A feeds of the same. Those power everything upstream that I need either constant or switched power for, and I never have to worry about overloading another potentially critical circuit.

PostPosted: Tue May 16, 2006 4:47 pm
by hacker_720
In terms to power locations, in almost all cases you have to run a new wire from your battery, if you piggyback something else you will probably blow the fuse, or you risk that 'something else' controlling whatever you just hooked up.

If you just need a signal to turn something on when the car turns on, I like to use the radio signal, since most of us have already hacked it apart. -maybe I’m not being clear:
most electronics that you put in your car will have three power connections, you will have +, -, and control... so I like to hook up the control to the control wire on the back of the deck.

Solder: heat up wire, not solder, touch with solder, let cool (5 sec) done.

To run wires in car, put along bottom of door under trim piece.

Ground, or anything metal in the car that touches the frame is (-)

Almost everything else is (+) or signal, black is not necessarily ground

So you only have to run a + wire to something.

Electrical tape will fall off when frozen (Canada)

Grounds may be the most important thing, make sure all grounds are good.

The inside of a wire may be broken even if the plastic is not.

If you have any electrical questions you can PM me. I’m on here all the time Monday-Friday.

PostPosted: Tue May 16, 2006 4:57 pm
by CMS-GT4
Thanks for the imput. I was hoping to get enough info together for a faq so there were not so many alltracs around that were an electrical mess.

So these blocks you mention Simba, could one be made and a single line run from it to various items in the car, or is something needed for every item?

Anyone interested in doing a pictorial writeup?

PostPosted: Tue May 16, 2006 5:03 pm
by hacker_720
The electrical blocks is like a power bar. You just install one and then connect everthing to it. Except insted of plugs there is just screw terminals, some power blocks have fuses in them, like simba's. There are different styles and different gages (AWG).

Simba- I thought I was the only one running powerblocks, nice to see someone else doing it right.

Don't know what you mean by a pictoral, not much with electrical needs pictures, I wouldn;t know what to point out. Maybe some more specific questions would help.

PostPosted: Tue May 16, 2006 5:13 pm
by CMS-GT4
Ok, so where would one get a power block. Electronic store or auto store? I have no idea what this stuff looks like.

When hooking up the block, does it go straight to the battery? Is there location related to the battery to wire to or to a battery post?

Where is the ignigtion switch that needs to be wired. I really wish there was a simple how to book to into car electronics.

PostPosted: Tue May 16, 2006 5:35 pm
by hacker_720
kinda looks like this ... sb6027.jpg

You would need to go to an electronics shop, or maybe a tuner shop, I don't think the big automtive guys have them, maybe you can check. It is a very simple device, just hook one of the wires to the battery, and the rest to wherever need power, all it is, is a chunck of metal wit a bunch of screw terminals on it, and a plastic case around it. the IGN switch that simbad is talking about is the same thing I was talking about with the radio.

I don't know how to explain it really esaly... I will get back to you.

PostPosted: Tue May 16, 2006 5:48 pm
by Snyder
I am in the same boat. Here is my link:

Here is situation:

I have a:

1. car alarm
2. AutoMeter 2 Channel Air Intake gauge
3. AutoMeter A/F gauge
4. AutoMeter EGT gauge
5. Turbo Timer
6. Etc.....

My ignition harness looks like a rats nest. Can someone draw a diagram to help us out. If you use that block and run a line from the battery to the block, those devices will always be on. Where does the relay come in to play?


PostPosted: Tue May 16, 2006 7:18 pm
by Gary
Here is an idea.
Using a distribution block and a Bosch 5-pin relay.
You can use other relays too.
But you need to adjust the wiring according to the pinouts.
You can choose to ground the relay and accessories individually like in the bottom diagram.
Note that 85 and 86 are switchable (non-polarity).




PostPosted: Tue May 16, 2006 7:22 pm
by Gary
Here is the distribution block that I'm planning to use.


PostPosted: Tue May 16, 2006 8:18 pm
by Simba
CMS-GT4 wrote:So these blocks you mention Simba, could one be made and a single line run from it to various items in the car, or is something needed for every item?

It depends what the electrical demands are, and how they're used. There's no easy "do it this way" when it comes to electrical wiring and load estimates, as every car and device is different. The general concept is to run one big power lead from the battery, through a large (50+ amp) fuse, to a distribution block with smaller fuses for various electrical devices.

This is my setup; the engine distribution block powers my fog and driving lights, IC fan, alarm sirens, and various other things. Some fuses have only one device on them (lights), some have more than one as they have a fairly small load. The large audio fuse runs into the car where I have another distribution block which powers all of my interior crap-- gauges, audio, boost controller, relay-actuation switches, etc, etc.

The bottom line is that you want whatever electrical bits you add to the car to be protected. 47 devices on a 50 amp fuse doesn't do you any good if one device on the chain blows up with 10 amps of juice.


PostPosted: Tue May 16, 2006 8:23 pm
by Simba
Gary wrote:Here is an idea.
Using a distribution block and a Bosch 5-pin relay.

It's a good idea, though I do mine a bit differently-- I run hot leads to the fuse block, then run the various relays I need after the fuses. That way I'm not pumping the full block load through a 30A relay.

More relays and more complexity, but no risk of cooked relays.

PostPosted: Tue May 16, 2006 10:48 pm
by ___Scott___
Just a tip for people who are adding relays, you can buy them through an electronics distributor a lot cheaper than through an auto parts store.

Here is one source where I happened to notice they are pretty cheap: Electromechanical > Relays > Automotive

PostPosted: Wed May 17, 2006 12:14 pm
by hacker_720
50-836H-0 $2.90
40AMP 12V.

I sell them, just tell me if you need some
You have to pay for shipping. Or you can just give me a credit card and we will add it to that.

PostPosted: Thu May 18, 2006 4:56 pm
by CMS-GT4
Thanks for all your replies. Looks like I am going to have to set this up to even finish my swap. I have to provide a power source to a curcuit to avoid my code 54.

Another question. My battery is in the trunk. On my positive terminal there is a small extra wire. Is this for adding a power block?

Since my water injection is setup in the trunk, should I have a second small fuse block back there coming from the battery, or just wire everything from the front of the car?