Live feed with ignition off

E

eggbert68b

Member
Hello - quick question please, given your experience in this area.

I'm looking for a 12V feed when the ignition is off, and off when the ignition is on.
I would like to fit a security device (flasher system) which is powered when the car is parked, i.e. with ignition-off,

Can you advise on an appropriate feed location.
Many thanks
 
You need a battery feed , from wherever is convenient, and a change over relay triggered by an ignition feed.
 
Thanks guys. the relay is a certainly a safe option as are fuses in the wires to the LED.

Thinking about it, there are some options..
You could wire the LED to the ignition switch, one side where the battery power comes to the switch, and the other side to any load that is disconnected by the switch.
The LED will be grounded by the Load that the ignition-switch disconnects.

Connect the LED between any circuit (fuse) that is live all the time (eg cigar lighter), and any circuit (fuse) that is switched by the ignition switch.
Here could be a need to include 2 ~1-Amp Fuses to protect the very small LED wiring, - 1 fuse for each wire as both are live.

the problem is that any DIY flashers tend to look DIY and hence may not be such a deterrent..
 
There is no feed which is on with the ignition off and off with the ignition on. You need a relay and use the normally closed (nc) terminals - these are often labelled "87a". As you need both a permanent live and the ignition, the place to do this would likely be from the switch itself. There are actually spare spade terminals for each on my ignition switch. Yours may be different. I took this for reference. The brown wire goes to terminal "1" which has a spare spade marked "X" as does the ignition - white wire which goes to terminal "2" and also has a spare spade marked "X".

85/86 go to +12 ignition (white terminal 2). and ground
30 goes to the +12V (brown terminal 1) permanently live
87a goes to your LEDs +ve and
87 is not connected.

Or you could wire it the other way take +12V ign to your LED - ground 30 and wire the negative side of your LEDs to 87a. Most automotive lighting does it this way but it does leave the cable live all the time. For example the interior light is always at 12V and the door switches and dash switch simply grounds the other side. which is obviously easier as you can ground it anywhere on the body rather than having 5 positive cables.


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Thanks Peter, this discussion and illustration is most useful and hopefully also of interest to others on the site.
Given the feed to the LED is live all the time, even with a relay do you advise using a fuse (1 amp) to protect the thin LED wires.

Thanks
 
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