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