12v positive when ignition off, please read.

[c2lby]

hi,

im looking for a 12v source which activates when the ignition is off and key removed and isnt live otherwise.

does this exist?

any suggestions anyone?

thx.

[richard@thebrae]

I would say No, but you can achieve it with a wee bit wiring and a relay.

[Doctle Odd]

Lighter?

[zollaf]

the lighter would still be live with ign on. ?

as above, easy to do with some simple electric bits and bobs but don't think you will find it otherwise.

[Doctle Odd]

I should have read it properly DOH!
the lighter would still be live with ign on. ?

as above, easy to do with some simple electric bits and bobs but don't think you will find it otherwise.

[trs888]

hi,

im looking for a 12v source which activates when the ignition is off and key removed and isnt live otherwise.

does this exist?

any suggestions anyone?

thx.

tough one, i had trouble finding ignition live when the key was in! found it tho in the end. sorry i was looking for the opposite! i just used trial and error tho!

[richard@thebrae]

There is only two options available as standard
a) constant live, or,
b) switched live when you switch on with the key (the cigarette lighter socket for example.)
To obtain a 12v source when the key is removed you will have to use a relay which in operation will pass 12v unswitched power (from say terminal 30 on the relay panel above the pedals as a possible source it is constantly live) to where you want it, and then the relay will breaks the 12v unswitched supply when you use the ignition key by applying switched 12v to the relay terminal that will operates the relay.(from say terminal 75 on the relay panel above the pedals or the ciggy lighter socket supply)
Turn off the ignition and the relay will close again and give you your 12v supply with no ignition.
Use appropiate wire and relays to carry the load you desire, and dont forget inline fuses

[Teflon]

Just out of interest, why? It just seems such a strange combination to want.

As others have said, yo can do it with a cheap relay, but make sure you use a NC version (i.e. open when energised). If you do it the other way around the relay curent might be enough to flatten the battery over an extended period.

You can't get the full version that will switch the power off when you pull the key without splashing out on a CANbus interface to switch the relay or doing something similar yourself using solid state components and a soldering iron. Good car hifi firms sell them or you can try eBay.

But a relay will give you what you want with the ignition switched off, which will hopefull be all you need.