12V port stays on when car is off

[DeutschRennfahrer]

I installed a radar detector in my Z4 yesterday, and was surprised to see that it wouldn't shut off when I turned off the car. Does the 12V port continue to provide power from the battery even when the car is off? I'd rather not have to power off the detector manually every time, so I'd love to know if there is a way around this. Perhaps the power gets shut off after I close and lock the doors, but I haven't tested this yet.

Thanks!

[XMetal]

That's normal. Most BMWs have live 12V ports. Why not hardwire it into either the fuse box or overhead light?

[seank]

Originally Posted by DeutschRennfahrer

I installed a radar detector in my Z4 yesterday, and was surprised to see that it wouldn't shut off when I turned off the car. Does the 12V port continue to provide power from the battery even when the car is off? I'd rather not have to power off the detector manually every time, so I'd love to know if there is a way around this. Perhaps the power gets shut off after I close and lock the doors, but I haven't tested this yet.

Thanks!

Always on. Kinda nice if you want to charge something while at work.

[ZStig]

Sorry for going off-tangent, but is there more than 1 fuse for the 12v port?

[RADRACR]

Get a fuse tap from ebay. Connect it to a fuse that is on only when the car is on (like A/C). Connect the ground to a metal screw near the fuse box. Make sure you get the right fuse type. If you don't want to cut up your wires, you can probably find a 12V socket on ebay too. Wish I could help you with the exact fuse to use but I've forgotten.

[RADRACR]

Originally Posted by seank

Always on. Kinda nice if you want to charge something while at work.

I've always worried about it draining the battery but do cars like ours prevent the battery from getting too low to start the car? I know there's aftermarket solutions for this.

[gas-can]

Another way would be to access the wires going to the stereo/console. There's an ignition wire in there that's 12v? when key is in. You can wire a small relay to that signal wire as a trigger and modify the cig's hot wire so that it only is live when the key is in. Probably will be the most OEM way to do it- plus if so inclined, you can revert everything back to stock when you sell the car...

Or you could just pull the thing out when you are done

-gc

[RADRACR]

^ Sounds more intrusive and complicated than the fuse tap.

[pokeybritches]

Fuse tap is the easiest. It saves you from splicing and soldering. If you're crimping versus soldering and heat shrinking when splicing, you're wrong. You can get away with crimping if you use a fuse tap and crimp to run a piece of equipment that's not critical, but all of the OEM wiring is critical IMHO, so I wouldn't recommend crimping if you splice into the existing wiring. I also don't like T taps. They're lazy and almost always tear up the wiring you're splicing into. That's why I say avoid it all and use a fuse tap.

[bgeorge0049]

+1 on the fuse tap.

[DeutschRennfahrer]

Interesting idea! I might wait a little while though cause I don't feel like forking out more money for the Escort hardwire kit.

My model will automatically shut off after 4 hours. Do you think it would cause harmful drain to my battery if I let it auto-shutoff after 4 hours?

[bgeorge0049]

Shouldn't drain the battery. Why don't you just pull the plug out of the cigarette lighter just before getting out and then put the plus back in when you get back in your car?

[DeutschRennfahrer]

^^^ That's what I have been doing, but I'd prefer to have it turn on and off when I start the car. It's not a huge deal though.

[pungo]

I believe there's a wire (purple w/ stripe) in the overhead light that is only on when the ignition is on.

[ShakyDog]

Originally Posted by pungo

I believe there's a wire (purple w/ stripe) in the overhead light that is only on when the ignition is on.

Yes, pop out the over head light and use a 3M splice to get the power to your RD, works great.

Steve

[DeutschRennfahrer]

That sounds easy enough. Any trick to pulling out the light fuxture?

[darknetone]

Did mine, bought an ATC add a circuit from autozone, 6$, soldered and liquid taped a sonar fuse spade. Checked the fuse bus, it it important to understand which side of the fuse supplies power.

[SD ///M4]

I found out that the 12V cigarette lighter port was live all the time when I was using a 12V/USB adapter for my phone. I left the adapter plugged in all the time and I went to remove it at one point and it fell apart in my hand. It was quite warm and the glue used to hold it together had melted. I'm glad it didn't start a fire overnight in my garage underneath two of our bedrooms!

I've since hard-wired a double-USB port into the panel below the HVAC controls which works great. I used a switched wire for the source.

Don't leave anything plugged into the 12V cigarette lighter port!

[DeutschRennfahrer]

Originally Posted by darknetone

Did mine, bought an ATC add a circuit from autozone, 6$, soldered and liquid taped a sonar fuse spade. Checked the fuse bus, it it important to understand which side of the fuse supplies power.

Can you explain a little more about what you did here? A fuse tap does seem like the easiest and cheapest solution, but I've never done this before so I'd really appreciate a step by step walk through if you don't mind.

[ShakyDog]

Credit card and push in on the two clips either front or rear to undo the light.

Steve

[darknetone]

OK so here is a little more info about how this works. Keep in mind that I did this to my 2003 Z4, however his is basically the same on other vehicles.

I checked the fuse box to determine where the power busses were and and to ensure I knew which were switched. I also chose to use the radio #74 (switched)and the cig-lighter (un-switched)#5.

From the attached drawing you will notice that power comes from the bottom connector for #47 and that this buss is switched. I could have used anything else on that bus but the radio has a low current draw and is non-critical from a safety/operational perspective.

Also from the drawing you will see that the the power buss come from the top connector for #5 the lighter. you want to stay away from the top connector, the bottom connector is what we care about since the bottom is where we want to provide power to.

So when we plug in the ATC -Add a circuit device we are taking power from #47 bottom pin and making it available to the #5 accessory pin.

I hope this makes sense, if not let me know.

[RADRACR]

^ Are you saying you converted the cig lighter to switched?