[Cdutch513]

I was wondering what I should do. I just installed a Pioneer AVH-X4500BT in my 2010 BMW 328i. It has the most basic sound system in it. Everything is working great but the constant 12V is not a true constant. It turns off after about an hour of the car being off. I was wondering if anyone knows what I can do without wiring running a wire all the way to the battery. Is there any fuse I can tap into? Please help!

[Cdutch513]

Please help!

[Ali-E90]

I had the same issue when I installed my pioneer double din also.

I searched and found the following:
http://www.e90post.com/forums/showthread.php?t=125203&highlight=aftermarket

Hint: searching will yield great results. There are many experts here, but they sometimes get frustrated answering the same questions over and over again (I don't blame them). Search then ask.

Good luck!

[Viktimize]

The more I read about this stuff, the more it seems like complete nonsense. If there is no true constant 12v in the dash, then where the hell does the stock headunit get it's constant power from?? I've never had an issue of getting into my car after a couple days of not driving it, and found my radio presets all gone. So there has to be a true constant 12v feeding it somewhere, unless the stock unit has some redundant back up battery source built in?

[bmw325i]

I would just run it off the battery.

[Ali-E90]

Stock unit is wired differently, as you can still turn on the radio even without a key in ignition. It does also have a a switched wire that turns the deck on and off when you do put the key in ignition.
After market HU are not wired that way, seems like the types of wires the stock unit uses and an after market one use are different.

[Cdutch513]

I figured it out you guys. I ran a fuse tap to the OBD fuse and its working fine.

[Viktimize]

Originally Posted by Ali-323i

Stock unit is wired differently, as you can still turn on the radio even without a key in ignition. It does also have a a switched wire that turns the deck on and off when you do put the key in ignition.
After market HU are not wired that way, seems like the types of wires the stock unit uses and an after market one use are different.

The stock unit would still require some kind of constant power supply to maintain it's settings. So it has to be fed constant power from one of the wires going in to the headunit. That's just a basic electrical fundamental. If you're saying there is a way to power the headunit while the key isn't even in the ignition, this proves the point even farther.

Somebody has to know about this? Does one of the computers store all the radio setting information, so that when it kills power to constant after a few hours, it reloads the info on start up?

[Ali-E90]

Originally Posted by Viktimize

The stock unit would still require some kind of constant power supply to maintain it's settings. So it has to be fed constant power from one of the wires going in to the headunit.

Agreed. My comment was just to show that it might not be a 1:1 mapping when it comes to Power and Ignition wires, as it often is in other cars.

[Viktimize]

Originally Posted by Ali-323i

Agreed. My comment was just to show that it might not be a 1:1 mapping when it comes to Power and Ignition wires, as it often is in other cars.

I've searched around on this for awhile, and I can't seem to find any info on it. Everyone seems to know that the constant 12v isn't a true source, but nobody knows why.