Find True Ignition Wire
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=133379
Printed Date: July 05, 2025 at 1:44 PM
Topic: Find True Ignition Wire
Posted By: krush
Subject: Find True Ignition Wire
Date Posted: January 21, 2013 at 5:02 PM
Hi guys i need some major help!!!!!
I'm looking for the true ignition wire on a 2007 Nissan Pathfinder LE 4x4 Bose wo/NAV.
reason is that my AVIC-Z130BT reboots every time i turn the key from acc to start the car. I only looking to keep the AVIC-Z130BT power on for the start. The 3 amps are going to be wire to a relay from the accessory wire from the OEM radio harness.( don't mind if the amp power off on the car start).
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The best tool in my work shop, is my BRAIN!!!!
Replies:
Posted By: DYohn
Date Posted: January 21, 2013 at 5:20 PM
Posted By: krush
Date Posted: January 21, 2013 at 5:54 PM
DYohn,
I have read that post when i was doing my search.
The problem is that when i start my car from the ACC1 Position, The starter cuts (voltage drops) the power to the red(ignition wire) for a few seconds and that causes the AVIC to reboot. Spoke to nissan tech, he told me that is so that all voltage is routed to the starter to start the car.
I have a metra wire harness installed. I tested the red wire and it dips below 5V when i start the car so i assume that is why the AVIC reboots???
Let me give a detail of the issue.
I went to fill up gas, so i turn the car off and had the key set at ACC1 to listen to the radio when the car was gassing up.
After the fill up i went from ACC1 (radio ON still) to start the car on the ignition. The radio reboots and it took 5 min for the VS Directory to rebuild/Nav. So do you see what I'm saying?????
sorry some times i don't put thought to text well.
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The best tool in my work shop, is my BRAIN!!!!
Posted By: soundnsecurity
Date Posted: January 21, 2013 at 6:19 PM
if your pathfinder is the same as my frontier then you should be able to find almost the whole ignition harness in a plug in the drivers kick panel. its the only plug with large gauge wires in it.
if the true ignition drops out during start then maybe you can used a relay that is wired to activate with the ignition AND starter wires so this way it will get power all the time. you would have to diode isolate the ignition and starter triggers to the relay to keep the ignition from feeding back to the starter wire but i think it could work.
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Posted By: Ween
Date Posted: January 21, 2013 at 7:29 PM
connect a multimeter in series (ammeter function) on the accessory lead.
measure current used with different sources, hopefully should be rather minimal. pick a diode with a value greater than maximum current measured, won't hurt to be generous and overrate the diode. next obtain
electrolytic capacitors, 25volt rated, start around 1000uF. wire diode in series on accessory lead, connect capacitor between accessory lead (head unit side of diode) and ground. the diode keeps the radio and capacitor isolated from the vehicle electrical system while the voltage drops, the capacitor supplies the radio with power. may need to increase the value of capacitance (add additional in parallel) depending on current requirements on the accessory lead of the headunit.
mark
Posted By: i am an idiot
Date Posted: January 21, 2013 at 7:33 PM
No need to measure the current. I will try to find the post with a diagram of what Ween was explaining.
The pic was drawn for a little different application. Read the post as well as looking at the picture.
Read this Thread
Posted By: krush
Date Posted: January 23, 2013 at 3:19 PM
Thx for the help guys!!!!
Is this correct?? Sorry didn't mean to plagiarism!!!!
 ------------- The best tool in my work shop, is my BRAIN!!!!
Posted By: i am an idiot
Date Posted: January 23, 2013 at 4:05 PM
That would be it. If that does not keep it on long enough, parallel a second capacitor, or just buy a 1000 microfarad device from jump.
Posted By: oldspark
Date Posted: January 23, 2013 at 4:37 PM
I was worried this was an issue of using ACC which dropped out during cranking (hence use 2 diodes, one from ACC and one from IGN as often done to keep relays energised from the ACC circuit powered during cranking).
But no, it seems to be a simple voltage drop whilst cranking issue and that circuit should work fine. [Noting the diode voltage drop of ~.6V or more but a Schottky diode can halve that; it won't hold up against longer cranks; and too large a capacitor will blow the diode (too much cap inrush current).]
But I like the Nissan tech's comment that it "is so that all voltage is routed to the starter...".
Say what? That circuit disconnects everything else except IGN?
Or does he mean the other IGN circuit is like the ACC circuit but is only on with IGN (not ACC, and not when cranking)?
With apologies... but I would have said the other IGN terminal drops unnecessary IGN stuff during cranking... etc. It doesn't "route more voltage", it removes loads so that cranking has more current available.
Posted By: krush
Date Posted: January 23, 2013 at 5:14 PM
Thanks much guys
IAAI, I'll stick with a 1000 microfarad to be safe.
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The best tool in my work shop, is my BRAIN!!!!
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