general motors switched power idiocy

I have had this problem several times and I'm just looking for a reason WHY.  I tap (typically) a brown wire that shows switched power at either the fuse box location, or ignition harness (because some idiot engineer thought it would be cool not to have switched power anywhere in their vehicles) but after I hook to it, the voltage dissappears.  What kind of circuit is this?  My hatred for American made vehicles is increasing every year.  Trailblazers, seem to be the worst.

What kind of current is your device demanding from the circuit?  You may need to use a transistor and a relay.  I will look for a post about your problem.

The above diagram will provide you 2 amps continuous current.  If you need more than that, you need to make the right leg trigger a relay.

And no, I am not the idiot that designed the new GM stuff.  That was another Idiot.