im installing a 2nd battery in my trunk, with an isolator relay (stinger SR200), but what do i use for the "true ignition source?" this wire must only have power when the engine is on, not when the battery is on, im at a loss on what i can use for this purpose, besides taking the column apart and searching through the ignition lock assembly...

 

a "true" ignition will have power with the key on, as well as while the engine is cranking. True ignition sources power things like the fuel pump, so try and find your fuel pump relay. If fox bodies they are under the drivers seat, not sure what year yours is again.

But thinking about this do you really want a true ignition for the isolator? That will allow the radio to be on while cranking and if you wired your battery right it should not effect the stock system but there really is no reason to have the radio on while cranking.

 

i wanted a TRUE IGNITION so the isolator relay would only turn on the trunk battery when the engine was cranking, so if the key is on, it does not allow the system to drain both batteries, but does allow the alt to charge both batts.... i need a wire with 12 volts ONLY when cranking.

my car is an 08 GT, just in case that matters!

thanks as always ttocs. when i post pics of the finished system, you, and my friend that built my sub box, will be given proper credit

 

I am confused....

There is only one wire that has 12v on it ONLY when cranking and that is the starter wire. if you find a true ignition it will have voltage on it while cranking, and when the key is on.