ACC/12v Wiring Diagram (EDIT: FULL diagram added)

**yuiou** · 05-12-2008, 01:01 PM

Below is a diagram that I made showing how the ACC signal will be distributed through the car. I have a relay circuit (aux-input mod) in the trunk, I will be feeding it power from the cig lighter. The amp gets a straight ACC signal and the computer gets a switched ACC signal. I set up a relay that switches power for my USB hub/DVD drive/Lilliput since I didn't want to give it a constant 12v or overload the cig lighter. The blue boxes are fuses and the numbers in them are amps.

Let me know if things look good and if my fuses are set up right. I'm using network cable (CAT-5, 24 gauge) since there are 8 wires in each cable. I used it in pairs in some places.

Thanks!

**DarquePervert** · 05-12-2008, 01:17 PM

1 - The cig lighter is NOT regulated 12v as you indicate.

2 - What is the relay circuit coming from the cig lighter used for? Your diagram indicates a circuit to nowhere.

3 - The fuses on the IGN line aren't necessary. They don't draw enough current to pose a danger. Granted, a fuse wouldn't hurt anything.

4 - A 120A fuse is probably overkill. I have a 100A fuse on 4AWG that powers a small inverter, the PC and two amps.

**yuiou** · 05-12-2008, 02:21 PM

1. I tested it, it gives a 12v when the ignition is in the first position. Is this not what regulated means?

2. Thats my aux-input to stock stereo mod. It doesn't relate to the diagram so I didn't include it. There are 4 relays wired together that switch inputs (L-,L+,R-,R+).

3. I know, but they are recommended on audio forums. What size should I use in each case?

4. Came with the kit I bought.

**FusionFanatic** · 05-12-2008, 03:31 PM

I tested it, it gives a 12v when the ignition is in the first position. Is this not what regulated means?

no, that is NOT what regulated means. the ACC line is "switched", not regulated...

a regulated circuit means that the voltage is regulated to stay within a certain range. the ACC and IGN circuits are switched, but get their power straight off the battery/alternator. this unregulated circuits are referred to as 12v, but the actual voltage flucuates, it can be as low as ~9v and as high as ~15v

**DarquePervert** · 05-12-2008, 03:58 PM

Originally Posted by yuiou

1. I tested it, it gives a 12v when the ignition is in the first position. Is this not what regulated means?

No.
Regulated means there is circuitry to provide a constant voltage. The car's electrical system doesn't provide regulated power.

2. Thats my aux-input to stock stereo mod. It doesn't relate to the diagram so I didn't include it. There are 4 relays wired together that switch inputs (L-,L+,R-,R+).

Don't know what this circuit is for, but I've never seen relays used for audio signals.

3. I know, but they are recommended on audio forums. What size should I use in each case?

My ACC line has no fuse.
I recommend being simple and using no fuse. If you want to be anal about it, use a 1A or 5A fuse.
Again... There is almost no current flowing on that line, so a fuse is really not necessary. Your devices are simply sensing the line and using it as a trigger, much the same as a relay.

4. Came with the kit I bought.

Like I said, it will work. If you get a fuse that is closer to the power draw of all the devices hung off that power line, it will provde better protection of the wire, IMHO.

**yuiou** · 05-12-2008, 04:09 PM

Great.

Sorry... switched, not regulated.

So can the ACC line be used to power that single relay I have set up?

Also, here is the relay circuit:

The only difference is that I'm putting on a switch on the 12v and not ground. Would it make sense to power these relays off the cig lighter so I don't over power the ACC line?

**yuiou** · 05-12-2008, 09:58 PM

Here is my final diagram for those interested. Hopefully this will give you guys a better idea of the fuses needed. The 150A fuse came with the kit and is already installed.

Input is appreciated. This is in a 1998 Lexus LS400, btw.