How do I make my cigarette lighter turn off with my car?

Question

I have a 2010 Ford Fusion. I am about to install a new Apple CarPlay sterero, and I also think it would be funny to install some custom horns. I need to power the buttons with the cigarette lighter power, but I don’t want to drain the battery when I’m away. How can I change my cigarette lighter power to turn off when the car is off without taking too much power from the battery? (I don’t know anything at all about electric work! The simpler the better. Thank you!)

? · Answer

Instead of using the lighter power, find a source that is already switched.

You may need to verify - but based on some Fusion forums, fuse #35 is a spare that is switched on/off with the ignition.

Anonymous · Answer

You want the power to be on to go to another button which is activated when you press it and only when you press it.  As soon as you let go it stops powering the horn.   It is the same thing for the stereo.  It only is on when the stereo is turned on.(meaning there is an on-off switch in the stereo.)  When not on= no battery drain. Really; I did this wiring on my own in the 70's

? · Answer

I agree with Coffee Drinker. The simpler, the better -> Buy a secondary battery and connect it to that battery. When the battery dies, charge the battery.

Robsteriark · Answer

Get an automotive electrician to install a relay into the feed which powers the socket. The relay will only switch the power on to the socket when it gets energised by a wire connected to a source which is only live when the ignition is on.

The lighter socket potentially has a high current draw and uses a thicker power supply wire than normal, so it’s not safe to wire it directly to an ignition live supply as they usually have thinner wiring rated for less current. The relay allows the thinner wire to act as a switch for the thicker wire.

If you knew what you were doing it would be an easy DIY job. But when you don’t know about car electrics you could cause a fire.

An automotive electrician shouldn’t charge much for the modification.

The Devil · Answer

Take up knitting. Have the stereo installed by a professional. Did you try the lighter yet with the car turned off to see if it isn't powered while the car is off?
Attaching a toggle switch is simple, and what to do if the lighter is always powered. Then again, you could choose a switched power source instead of the lighter

Coffee Drinker · Answer

If you "don't know anything about electric work!" and need the instructions to be "the simpler the better"

then you probably shouldn't attempt to customize and modify the electronics on your car.

How do I make my cigarette lighter turn off with my car?

6 Answers