Power relay switch while ignition switch is "ON"
 

Could anyone help me locate an "ignition on" to power a relay switch?
Suppose it should be on the wire harness behind the glove box.

anyone....? :(

use either of the Cig lighters -- those are the easiest, if not then use the fuse box on the lower left of the driverside

I used the power from the "foot lights" (my car is used and came with those light preinstalled).
To put things down this is my case:
1) I have a carpc installed in the trunk. I am feeding it from the power source this is on the centre armrest.
2) I want to install an SLA battery (7,5Ah) in the trunk and have it connected to the carpc to survive cranking.
3) if I install the battery directly on the line POWER SOURCE-->SLA BATTERY-->CARPC when I switch off the car and step out and even lock the car the stereo headunit remains ON with the speakers working. If I unplug the battery everything's fine.
and here is my last point
4) I decided to install a small relay switch to control WHEN to power the carpc with the SLA battery. Unfortunately the wires from i am "reading" now have the same effect.

Therefore, I need a source that will switch power off the rear power source no matter if the power source is feeding a device with power.

I hope I state my problem clearly.

Thanks!

Diode.....
 

You probably need a diode.

If you put a good diode in the line to the battery, it will charge it when the ignition's on, but the power from the battery won't be able to go back down the line and "backfeed" the rest of the car.

S

Thanks for your help!