12 volt wire loses voltage

I am installing an anti theft device in a 2008 charger.  Everything is fine except one thing.  The wire I am using as my trigger voltage shows 12 volts all of the time when the key is on.  The problem is when I touch the input wire from my product to the 12 volt output, the voltage drops down to 0 volts.  When I remove the wire it pops back up to 12 volts.  Several 12 volt wires on this car do the same thing.  Is there anything I can put in between the 2 wires to prevent this voltage from dropping out?

Thanks in advance !

there may be something wrong with the actual product.

sounds like your 12v input to your product is ground.  Whenever you touch it to 12v, it goes to ground.  Either it's the wrong wire, or there's something wrong with your product.

You need to use a transistor.  I will have some time tonight to draw you a diagram.  There is not enough current capacity on that wire that you are using.  You will have to use it to turn on the transistor.  You can get about 2 amps of current using the transistor only, if you need more current you will have to use the transistor to power a relay.

Thanks enice I was thinking that way, are you trying to connect an ign sense or the ign in break. If it's the former you definately have a short to ground sence the ign. sese wire on an immobiliser at most has to trip a relay or (2 x relay) coil. Craig, nice to see you floating back! sorryh every pun intended.

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Thank you guys !  I am using the wire to sense when the ignition key is on.  And as I stated when I touch my input Sense wire to the 12V output wire I chose,  the voltage drops to 0V.  I will try the transistor.  I will have to use a relay with it however because I think the circuit will draw between 3-15 amps.  Thanks again !

Mike

I'm getting worried about this, the ign sense should draw next to nothing, place the unit across a 12v  battery and connect the grounds. Then connect this wire to the pos. You should see nothing at the terminal. If you get lots of sparks its faulty, don't use it.

Have you connected your grounds BEFORE you hook up the 12volt positive.  I had a 07 Jeep Patriot (Jeep/Dodge....same thing) that I worked on last thur, and when I hooked the 12 volt positive wire to the ignition wire it was doing some weird things.  Figured it was something with the ground and hooked that up first....then reconnected my ignition wire and sure enough.....no weird stuff!  Make sure your grounds are hooked up first!!!!