# Prevent a reset when starting the car.



## fuji6 (Feb 4, 2008)

I recently installed a navigation system in one of our cars. I'm not sure if this is an install issue, caveat or what. 
Here is the problem, if get in the car and turn on the raido without starting the car (accessory key position), then start the car. The Head unit will turn off and back on rebooting itself. I noticed that happened with the previous head unit, but it wasn't an issue since the start up time was significantly faster. 
Is there any known work around for this?

Here's where it's commonly an issue for me. I'll drive someplace to pick somebody up. While I wait I have the radio on, but the car off. When I start the car it will reset and I have to wait for the system to reboot.


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## F1Audio (Jun 5, 2009)

I know what you mean. I think it is vehicle dependent as I have had some where this did not happen. I think on most vehicles, when you turn the ignition to the start position, it disengages the accessory power. I am sure there has to be a way around this....maybe as simple as wiring a capacitor inline with the ACC. line on the head unit?


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## Austin (Mar 12, 2009)

One way that wont be convenient is to make your own ignition wire with a switch on the dash...that way it wont turn off when you start the car and you dont even need your key to use it!


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## 12vTools (Jan 15, 2009)

accessory wires drop their voltage during crank
Ignition wires maintain voltage during crank 


meter to be sure and change your accessory wire to a true ignition and you shoukd be set.

HTH


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## fuji6 (Feb 4, 2008)

Thanks for the replies. 
I was afraid that was going to be the answer. I really wanted to avoid adding more wires behind the dash. 

Are there any potential dangers in changing to a true ignition source? I'm sure it's factory this way for a reason.

Thanks again.


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## 60ampfuse (May 18, 2008)

g0a said:


> accessory wires drop their voltage during crank
> Ignition wires maintain voltage during crank
> 
> 
> ...


Bingo! All you have to do is take the red wire from the navigation, disconnect it from the acc, tape off the acc so it doesnt short, and run the navigations red acc wire to the vehicles ignition wire.



fuji6 said:


> Thanks for the replies.
> I was afraid that was going to be the answer. I really wanted to avoid adding more wires behind the dash.
> 
> Are there any potential dangers in changing to a true ignition source? I'm sure it's factory this way for a reason.
> ...


The only disadvantage would be that where you normally sit and wait with the car in the acc position you would now have to wait in the ignition position. Which will kill the battery quicker. ESPECIALLY if its made by GM.


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## Abaddon (Aug 28, 2007)

You could also rig up a fancy holding circuit with a relay and a timer 

Most complex solution, but it would be fun to do.


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## monkeyboy (Jun 12, 2007)

only downside is that if you get out without turning it off, you battery will be drained. The acc shuts down my system after I get out. No thinking necessary.


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## 60ampfuse (May 18, 2008)

The best way to do this is to add whats called a retained accessory for the radio. If you are pretty good with electrical work you can probably do it yourself. If not, I would take it to a car audio shop. All you need is two relays. I doubt most shops would charge more than about $75 for the labor. This will cause the radio to always be turned on untill a door is opened (it will still stay on while the engine is cranking unless a door is open). Most vehicles only have the radio turned on while in acc. If your vehicle has multiple devices turned on in the acc position then you will need 3 relays and some diodes. Not really a big deal just will cost you a little more. Here is a diagram.
Special Applications with SPDT Relays, Diagrams
What kind of vehicle is it?


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## fuji6 (Feb 4, 2008)

It's a Subaru wrx 09.

Hmmm, I'd prefer just a delay so it didn't reset during cranking. The whole door thing seems like something beyond the scope of what I'd want to do.


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## 60ampfuse (May 18, 2008)

Well the retained accessory is kind of cool too tho, just like most new cars these days keep the radio turned on untill you open a door, this would be the same thing. You can have a shop do it for you.


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## fuji6 (Feb 4, 2008)

Yeah it is a kind of cool. I may actually go that route after viewing the diagram it doesn't look complicated at all. I want to make sure I completely understand how it works before proceeding but, it's definitely something I'm going to take a close look at.

Thanks for the link.


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## Austin (Mar 12, 2009)

60ampfuse said:


> Special Applications with SPDT Relays, Diagrams


That remote start relay system is CRAZY!

10 relays all wired up...


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## 60ampfuse (May 18, 2008)

Austin said:


> That remote start relay system is CRAZY!
> 
> 10 relays all wired up...


Yup, but also unsafe and unreliable. It has no protection and no way to know if the car is actually running or not. I would strongly advise anyone against it  (especially with the cheap price or remote starters now a days).


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## maclouie (Apr 15, 2014)

There are a couple reasons why a head unit resets. 1) the "acc"momentarily loses power when engine is cranked by design; 2) if head unit is connected to ignition or "on" and head unit still resets it's because the battery voltage drops below 10.5V (some Kenwood units will reset if battery voltage goes below 10.5V). Also, if connected to "on" the radio will turn off when you turn your engine off - bummer. 

I am working on a simple to install $40 solution to keep unit on even during crank and even after turning engine off (when key is in acc, on, and crank positions and even if battery voltage drops to 8V). Downside is it may take battery energy away from crank but you can always turn your radio off if engine is hard to crank on cold days.


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