12V Power outlets - switched?

[maffud]

It appears that the 12V outlets in my 2008 A4 are always powered, even when the car is off. I thought maybe they would turn off after an hour like the radio, but that does not seem to be the case.
Has anyone successfully re-wired the outlets, or one of them, to be switched with the ignition so there would be no fear of running down the battery with a GPS or other device? Could anyone offer tips on where to find a switched power line near the front outlet to re-wire it?
I tried searching but didn't see anything addressing this particular issue.

Thanks!
Dan

[Stubek]

Not sure about the B7, but the owners manual for my B6 said something about a battery run down protection system that if the car detects the battery getting too low, it automatically disconnects the 12volt outlets then a few other things. I left my iPhone plugged in for more than two weeks while my car was parked at the airport accidentally. The car had more than 80,000 miles on the original battery that was more than 7 years old. I came back and the phone was fully charged and the car started the first try

[maffud]

OK, so I admit I'm not really too concerned about running down the battery. I'm not surprised that there is protection for that situation.
I use a GPS that will automatically turn off when the external power is cut, and I would like that to happen when the car is turned off. I guess it's more of a convenience than anything else. I know lighter jacks used to be constant power on all cars, but I've become accustomed to having switched outlets, so I would like to re-wire at least one of them to be that way. Surely, I'm not the first one to want to do this...?

[JPT]

I want to do this too... and might eventually after my CPO is up. Find a switched wire, and run that to a relay, with the power coming directly from the battery.

You can just use a voltmeter, turn the key on and off looking for a switched source.

[maffud]

If you use a relay, you could just use the same fused line the outlet is on now for the power. Maybe that's what you meant.
Anyway, not sure about just "using a voltmeter" to find a switched source. I mean, I know how to use a voltmeter, but you have to cut through the insulation or find an end to determine whether or not a wire is supplying switched power. Not about to go cutting into random wires under the dashboard for this.

I guess the question is: what devices under the dash get power only when the engine is running? Normally, this would be the radio, but somehow I don't think that's the case with this car.

[JPT]

I would run it directly to the battery with a larger gauge wire. This way I wouldn't have to worry about overloading that circuit... (without the wiring diagram, I have no idea if the factory shared that wire with other components.

You don't have to cut the insulation of the wires, trace to the end of each wire in the area, and unplug it.

But since I intend to pull the power directly from the battery, I would have the relay under the hood, and pull the switched source from under there, not under the dash area. This way, the only wire that is run to the lighter, is the switched relayed 12V heavier gauge wire... and depending on the gauge ground wire, I might run a new ground of matching gauge or the newly run 12v wire.

And if you go this route (I don't blame you if you don't) don't forget an inline fuse on the 12V power line, at the rating you want for devices you use. This is the proper way to wire it, especially if you intend to use more amps, then the original design.

[maffud]

I don't think I am going to be using the outlet for anything that would overload the circuit. Just plugging in a GPS or a cell phone. There is a fuse labeled specifically for the power outlet, so I am guessing there is nothing else on it, anyway. Although as you said, without a wiring diagram or tracing the wire from the fuse box to the outlet, there's no guarantee that it's not also supplying something else. I guess I am willing to take that chance.

I played with the voltmeter at the fusebox a little last night and found that the garage door opener circuit is a switched source. So currently my plan is to run a short wire from that fuse to a relay, which would open/close the circuit that runs to the outlet. I think I could do all of this right behind the fusebox, where it looks like there is quite a bit of available space to use. This way the outlet fuse still does what it says it does and I am only drawing a tiny additional current off of the garage-door opener circuit to run the relay.
I'll do some searching and hopefully find some info about accessing the back of the fuse box. If you happen to know of a good DIY article about that, shoot me a link. :-)

[JPT]

Sound like a good plan. Please take pictures, and document what you are doing... There are tons of us that are interested in this. When I do mine (years from now), I will do it the way I plan, and will also do a writeup.

[maffud]

A quick update. I've not done the mod yet, but I will do it either tonight or this weekend. I did take the lower dash cover off to see what I would be dealing with behind the fuse panel. The wires coming out of the fuse panel are pretty tightly bound up with very little slack. I was going to tap into the wire for the homelink circuit behind the panel, but I am now going to use a piggy-back "add-a-fuse" device in the front of it, instead. The only "damage" I will do to the OEM stuff will be cutting the wire to the front power outlet in order to send it through the relay. I found a good ground (I think) behind the fuse panel with a bolt that appears to go right into the chassis to use for the relay coil circuit. I will have some pics and full details to post up when it's all done.

[maffud]

I got this done today. I almost didn't post about this because I am embarrassed that I initially put the relay on the wrong wire (making the arm-rest outlet switched instead of the outlet next to the ashtray). But I'm going to chalk it up to the 100 degree heat I was working in today. Yeah, that's it.

Here are the parts I used:

1. 12V NO (Normally Open) automotive relay. These can be obtained from radio shack or probably a car-parts store, but I got mine from digi-key for less than $6 shipped. (Clicky)
2. about 2 feet of 12-gauge insulated wire. Frankly, I'm not sure exactly what gauge my wire was, but it seemed to be about the same as the power wire that I was cutting. I used some red and some black to ease identification.
3. 4 female spade connectors
4. 1 U-shaped connector for the ground wire
5. 3 10-12 gauge butt-end connectors
6. I also used another pair of spade connectors, but I realized when I was done that this was not necessary.
7. 1 mini fuse add-a-circuit. I used LittleFuse part #FHM200BP from the local Checker (Now O'Reilly) Auto store for $6.99. (Clicky)
8. 1 large tie-strap (to replace the OEM one that will be broken)
9. 1 smaller tie-strap for the relay wires
10. Electrical tape.

Some of the parts:


Before starting on the car, you can wire up the relay. I used red wires for live wires, and black for the ground.
2 shorter lengths of red wire (about 6") with a female spade connector on one end of each. Mark one as "Outlet IN" and one as "Outlet OUT."
1 longer length of red wire (~ 1 foot) with a female spade connector on one end. Mark as "Switched Source". You can connect the other end to the add-a-circuit lead now, although I did that after wiring up the relay in the car.
1 longer black wire (~ 1 foot) with a female spade connector on one end and the U-shaped connector on the other end.

The "switched source" will go on the terminal marked as the coil source positive or high. The black/ground gets the negative/low coil terminal.
Connect the IN/OUT wires to the switched terminals on the relay. I don't think it matters which direction the outlet current goes through the relay.


After wiring it up, there is too much exposed current-carrying metal for my tastes, so I taped up the connectors individually, then tie-strapped them together and taped them all up to provide some strain-relief.



Before doing anything to the car, disconnect the battery!

Next, you need to take the cover off the side of the dash to expose the fuse panel. Then you drop the lower dash panel.
There are just 3 bolts to remove from the panel, one on either side of the steering wheel and one just above the fuse panel. Remove the bolts, then gently pull the panel away from the dash and lower it to the floor. No need to remove the wires connected to it, but you can if you want to get it completely out of the way.

The fuse panel exposed, with the lower dash panel dropped.


Next, remove the two bolts from above and below the fuse panel to separate it from the chassis. Then pry the tabs to open the back cover of the panel. In the picture. I actually pulled the whole back cover off. I didn't break it to get it off, but it's not necessary.


Use small wire cutters to cut the plastic tie strap at the base of the panel to get more play in the wires.

Find the red wire with blue stripe going into fuse slot 34. The slots are numbered on the back, but it's pretty hard to see them. This is part of the reason why I first cut the wrong one. The one I initially cut was red with a gold stripe, and that one is for the arm rest outlet. The one for the front outlet is red with a blue stripe, and it connects to the slot smack in the middle of the block of larger fuses.


Now you need to cut that wire. Make sure you're cutting the correct wire! Strip off some of the insulation from both new ends.
Now, I think I put the relay on the source side of the circuit, which is probably not the ideal solution, but I just could not get to the other side of the fuse. It still works, but theoretically, there is more risk of non-fused shorts this way, I think.

Using the butt end connectors, (or solder and tape or other insulation if you're braver than I am with a soldering iron), connect the relay. On the wire going back into the car, connect the wire marked "outlet OUT". On the wire going to the fuse panel, connect to the wire marked "outlet IN".
Connect the black ground wire under the silver-covered nut located to the right of the fuse panel just under the steering wheel, or any other good ground location you can find.


Try not to be distracted by the extra wire patch in here from the wrong wire that I cut.

I used the smallest (3-amp) fuse that came with the add-a-circuit for the relay.
Remove the fuse from the slot for the garage door opener (I forget the number, but it's the top right corner fuse in the panel) and put it into the add-a-circuit. Then put that into the now open slot in the fuse panel, with the lead going to the right.

Make sure the connections are secure. Re-connect the battery terminals and make sure everything works as it should.

If everything works, disconnect the battery again. Pull out the add-a-circuit device, replace the tie-strap at the base of the panel, put the back cover on the fuse panel and re-install the panel into the chassis. Then thread the add-a-circuit lead back through to the front of the panel and re-insert into the panel. I used the extra spade connectors in the line from the add-a-circuit to the relay, but it's really not necessary since it's easier to just it out of the fuse panel. Also, I had to tape up that spade connection anyway to prevent it from grounding against some part of the chassis.

I just left the relay hanging under the dash. It just sits on the insulation on the dash panel - no worries there. Replace the dash panel (threading the screw to the right of the steering wheel is the hardest part of this whole thing).

Here is what it looks like after the dash panel is replaced:

Note that I tucked the wire behind the chassis so it wouldn't get pinched between the chassis and side dash cover.
Replace the side dash cover.
Reconnect the battery one last time and you're good to go. Your front power outlet is now switched.

Wow. It took me longer to write this up than to do the work, I think.
If anyone else does this, please let me know so I don't assume this was all a waste. :)

[JPT]

Nice... it wont be a waste... I still plan on going direct to the battery, but if that turns out to be overkill when I am wiring it I will do the same as you. But this will be years from now after CPO ends.

Thanks for the writeup.

[martin0079]

I really dont consider this to be a big issue because I would not leave my gps plugged in or stuck to the window due to my brother having his window smashed out and his gps stolen. Just something to keep in mind.

[maffud]

I never said it was a big issue. Just a very minor annoyance for me. I did it mostly to prove to myself that I could. My car is garaged, so the GPS is usually left mounted and connected.

[JPT]

I would rather be able to leave my cell phone charger plugged in all the time, rather then have to plug it in when i need it.

I only drive my car on the weekends, I take mass transit to work, so my car sits 4-5 days every week...

This is a very good mod!!!

[chrisftl]

there's an easy way to do this that is absolutely free and requires no know-how whatsoever!

turn off your ish before you get out of the car, or unplug your devices. -____-

seriously. my dad has had to replace the battery in the porsche twice in 30,000 miles because both he and my mom ALWAYS leave the goddamn gps on and plugged in (EDIT) and because they rarely drive it.

[martin0079]

there's an easy way to do this that is absolutely free and requires no know-how whatsoever!

turn off your ish before you get out of the car, or unplug your devices. -____-

seriously. my dad has had to replace the battery in the porsche twice in 30,000 miles because both he and my mom ALWAYS leave the goddamn gps on and plugged in (EDIT) and because they rarely drive it.

Havent your mom and dad heard about charging the battery I have drained alot of batteries but it never caused an early failure on the battery

I never said it was a big issue. Just a very minor annoyance for me. I did it mostly to prove to myself that I could. My car is garaged, so the GPS is usually left mounted and connected.

Just becareful with leaving the gps showing is all I am saying

[chrisftl]

Havent your mom and dad heard about charging the battery I have drained alot of batteries but it never caused an early failure on the battery

forgot to mention they also had a radar detector plugged in. either way, the battery was shot. but it sat for months to be fair both times that it happened. they learned from their mistakes (except my dad that *thinks* the gps in his truck turns off automatically), but it's so easy to avoid, a mod like this seems unnecessary. is it really that much of a hassle to unplug your phone charger and stick it in the center console 'till you need it? or unplug your gps and just leave it there and plug it in when you start up the car?

[doowopaudi]

I got this done today. I almost didn't post about this because I am embarrassed that I initially put the relay on the wrong wire (making the arm-rest outlet switched instead of the outlet next to the ashtray). But I'm going to chalk it up to the 100 degree heat I was working in today. Yeah, that's it.

Here are the parts I used:

1. 12V NO (Normally Open) automotive relay. These can be obtained from radio shack or probably a car-parts store, but I got mine from digi-key for less than $6 shipped. (Clicky)
2. about 2 feet of 12-gauge insulated wire. Frankly, I'm not sure exactly what gauge my wire was, but it seemed to be about the same as the power wire that I was cutting. I used some red and some black to ease identification.
3. 4 female spade connectors
4. 1 U-shaped connector for the ground wire
5. 3 10-12 gauge butt-end connectors
6. I also used another pair of spade connectors, but I realized when I was done that this was not necessary.
7. 1 mini fuse add-a-circuit. I used LittleFuse part #FHM200BP from the local Checker (Now O'Reilly) Auto store for $6.99. (Clicky)
8. 1 large tie-strap (to replace the OEM one that will be broken)
9. 1 smaller tie-strap for the relay wires
10. Electrical tape.

Some of the parts:


Before starting on the car, you can wire up the relay. I used red wires for live wires, and black for the ground.
2 shorter lengths of red wire (about 6") with a female spade connector on one end of each. Mark one as "Outlet IN" and one as "Outlet OUT."
1 longer length of red wire (~ 1 foot) with a female spade connector on one end. Mark as "Switched Source". You can connect the other end to the add-a-circuit lead now, although I did that after wiring up the relay in the car.
1 longer black wire (~ 1 foot) with a female spade connector on one end and the U-shaped connector on the other end.

The "switched source" will go on the terminal marked as the coil source positive or high. The black/ground gets the negative/low coil terminal.
Connect the IN/OUT wires to the switched terminals on the relay. I don't think it matters which direction the outlet current goes through the relay.


After wiring it up, there is too much exposed current-carrying metal for my tastes, so I taped up the connectors individually, then tie-strapped them together and taped them all up to provide some strain-relief.



Before doing anything to the car, disconnect the battery!

Next, you need to take the cover off the side of the dash to expose the fuse panel. Then you drop the lower dash panel.
There are just 3 bolts to remove from the panel, one on either side of the steering wheel and one just above the fuse panel. Remove the bolts, then gently pull the panel away from the dash and lower it to the floor. No need to remove the wires connected to it, but you can if you want to get it completely out of the way.

The fuse panel exposed, with the lower dash panel dropped.


Next, remove the two bolts from above and below the fuse panel to separate it from the chassis. Then pry the tabs to open the back cover of the panel. In the picture. I actually pulled the whole back cover off. I didn't break it to get it off, but it's not necessary.


Use small wire cutters to cut the plastic tie strap at the base of the panel to get more play in the wires.

Find the red wire with blue stripe going into fuse slot 34. The slots are numbered on the back, but it's pretty hard to see them. This is part of the reason why I first cut the wrong one. The one I initially cut was red with a gold stripe, and that one is for the arm rest outlet. The one for the front outlet is red with a blue stripe, and it connects to the slot smack in the middle of the block of larger fuses.


Now you need to cut that wire. Make sure you're cutting the correct wire! Strip off some of the insulation from both new ends.
Now, I think I put the relay on the source side of the circuit, which is probably not the ideal solution, but I just could not get to the other side of the fuse. It still works, but theoretically, there is more risk of non-fused shorts this way, I think.

Using the butt end connectors, (or solder and tape or other insulation if you're braver than I am with a soldering iron), connect the relay. On the wire going back into the car, connect the wire marked "outlet OUT". On the wire going to the fuse panel, connect to the wire marked "outlet IN".
Connect the black ground wire under the silver-covered nut located to the right of the fuse panel just under the steering wheel, or any other good ground location you can find.


Try not to be distracted by the extra wire patch in here from the wrong wire that I cut.

I used the smallest (3-amp) fuse that came with the add-a-circuit for the relay.
Remove the fuse from the slot for the garage door opener (I forget the number, but it's the top right corner fuse in the panel) and put it into the add-a-circuit. Then put that into the now open slot in the fuse panel, with the lead going to the right.

Make sure the connections are secure. Re-connect the battery terminals and make sure everything works as it should.

If everything works, disconnect the battery again. Pull out the add-a-circuit device, replace the tie-strap at the base of the panel, put the back cover on the fuse panel and re-install the panel into the chassis. Then thread the add-a-circuit lead back through to the front of the panel and re-insert into the panel. I used the extra spade connectors in the line from the add-a-circuit to the relay, but it's really not necessary since it's easier to just it out of the fuse panel. Also, I had to tape up that spade connection anyway to prevent it from grounding against some part of the chassis.

I just left the relay hanging under the dash. It just sits on the insulation on the dash panel - no worries there. Replace the dash panel (threading the screw to the right of the steering wheel is the hardest part of this whole thing).

Here is what it looks like after the dash panel is replaced:

Note that I tucked the wire behind the chassis so it wouldn't get pinched between the chassis and side dash cover.
Replace the side dash cover.
Reconnect the battery one last time and you're good to go. Your front power outlet is now switched.

Wow. It took me longer to write this up than to do the work, I think.
If anyone else does this, please let me know so I don't assume this was all a waste. :)

Interesting. Here you are doing what all of our A4 B8's come with and almost everyone who went from the B7 to the B8 is trying to get it back to the way it was on the B7's, that is, to have constant power on the 12v power outlets and no one has a clue as to how.

[maffud]

Interesting. Here you are doing what all of our A4 B8's come with and almost everyone who went from the B7 to the B8 is trying to get it back to the way it was on the B7's, that is, to have constant power on the 12v power outlets and no one has a clue as to how.

In other words, Audi's team of experienced engineers realized that it is better to have the outlet switched just as I did, and now the car comes like that from the factory. I have to assume that "almost everyone' is at least a BIT of an exaggeration. :-)

[doowopaudi]

In other words, Audi's team of experienced engineers realized that it is better to have the outlet switched just as I did, and now the car comes like that from the factory. I have to assume that "almost everyone' is at least a BIT of an exaggeration. :-)

Lol..yes, it is an exaggeration, however, I do find it inconvenient to not be able to leave my phone charging in my car while I'm inside the store or restaurant. There are a couple of DIY's in our sub-forum that explain how to get constant power, but no pictures. :(

Another thing about the B7s that B8s (not equipped with Navigation) do not have is the ability to keep the radio on until either the key is removed or the door is opened. We have to manually restart the radio with the car off and even then, it will only stay on for about 10 minutes. Again, those who have B8s with navigation do not have this issue.

[PNW Avant]

Lol..yes, it is an exaggeration, however, I do find it inconvenient to not be able to leave my phone charging in my car while I'm inside the store or restaurant. There are a couple of DIY's in our sub-forum that explain how to get constant power, but no pictures. :(

Another thing about the B7s that B8s (not equipped with Navigation) do not have is the ability to keep the radio on until either the key is removed or the door is opened. We have to manually restart the radio with the car off and even then, it will only stay on for about 10 minutes. Again, those who have B8s with navigation do not have this issue.

I don't know about you but i would be pissed off if I had to turn off my car THEN turn off my radio every time. I like the way my RNS-e is set up in my B7 - turns off when I turn off the key. If i want to turn it back on, just hit the power button and it comes on even if the key is not in the ignition. I haven't sat there longer for 10 min to see it turn off, either. Works great for me.

[Jay-Bee]

I haven't sat there longer for 10 min to see it turn off, either. Works great for me.

I'm sure the RNS-E isn't any different than the Synphony 2+, you get 10 mins of power without the keys in.

I want to hard wire my radar detector in, and have the power line come out my center dash vent right below it... I have a Whistler XTR something and it has an auto shut off after 30 mins, never had it kill my battery, but i'd like to have it switched, i'll come back to this thread when i can do it.

I also now work at an electrilcal hardware wholesaler, cable and accesories for dirt cheap!

[tbaudi]

Almost 13 years later and I am getting ready to do this on my '05 S4 Cab so the add on AA/Carplay device isn't on all time, thank you!