Calbe With Power When Car Is Off

[zpybar]

I´m looking for a cable that gives 12v when the car is off.

My idee is to install a blue-diod that flashes like an alarm diod.

The thing is I want it to start flashing when I turn the ingition off.

Diod on when car´s off. Diod off while I´m driving.

So is there any cable that only gives power when ignitions off?

Excuse my English, skipped some lesons :P

[matty_aygo]

well pin 7 in the back off the HUnit is the live 12v feed so anything into there will be powered when then car is off (learned that the hard way)

easist way to do would to just put a switch on it to turn it on before you leave the car or sumit.

[Jan van de Wouw]

If you connect he LED with positive at the +12V behind the radio and the negative

side of the LED to +12V with the ignition on it will work like you descibed.

It might sound stupid to connect this to two positives, but you can trust me; it works.

So Anode of the LED (long leg) goes to A4 (permanent 12V) and Cathode

(short leg, flat spot on LED-housing) goes to A7 on the ISO-connnector.

[BadBoyVTEC]

If you connect he LED with positive at the +12V behind the radio and the negative

side of the LED to +12V with the ignition on it will work like you descibed.

It might sound stupid to connect this to two positives, but you can trust me; it works.

So Anode of the LED (long leg) goes to A4 (permanent 12V) and Cathode

(short leg, flat spot on LED-housing) goes to A7 on the ISO-connnector.

Are you sure this will work? How can the Ignition turn into a negative terminal when it is off? Have you tried and tested it?

[Jan van de Wouw]

Are you sure this will work? Have you tried and tested it?

About 95% sure. I haven't confirmed this on an Aygo (yet),

but I had a similar setup in both my Ford Escort and my brother's Landcruiser.

How can the Ignition turn into a negative terminal when it is off?

Actually it doesn't. What happens is that with the ignition on, the LED

gets +12V at both ends, so no current can flow and it won't light.

However if you turn off the ignition, the LED sneaks the little current

it needs to light though all the other things that get their power the

instant the ignition is turned on, like ECU's, the radio and the like.

In essence the LED is wired in SERIES with the other things,

but the tiny amount of current it uses isn't enough to power these...

This is a very simple fact that's used in cars quite often actually.

Some aftermarket light reminders need to be connected between

a wire that's +12V with lights and one with +12V after ignition.

When both are on nothing happens. Only igniton on does nothing because

of a diode in the circuit, but with only lights on the buzzer sounds...

And on my DeLorean I used the same principle to get the side marker lights

at the front to work as both side lights as well as side indicator repeaters.

The neat thing with that mod was that because it used incandescant

bulbs instead of LEDs the effect worked in 3 ways:

Lights on / Indicators off: side light lit

Indicators on / Lights off: side light blinks WITH indicators

Indicators On + Lights on: side light ALTERNATES with indicators:

when the indicators light the side light goes off...

You might also have seen this effect on lorries;

these sometimes have little lights at

the back on rubber sticks like these:

It's quite common to wire these between the

indicators and taillights like described above...

This Smart is wired like this too:

the difference in timing for the front and side lights is due to the difference

in wattage for the bulbs; smaller bulbs (4W) heat up different because of their

higher resistance, so they don't run in EXACT sync with the fonts which are 21W

The principle for the fake Alarm-LED is the

same, only the application is different.

If you need more explanation let me know, so I can

draw you a flowdiagram for the currents involved...

[Jan van de Wouw]

And? Did you try? It worked, didn't it?!

[zpybar]

I´m going to try tomorrrow, I have been sick = no time.

Hope it works ;) I´ll write when I´m done.