How to find ignition wire for car stereo setup

” Hi , can you please tell me how to know which wire is the ignition wire when wiring the stereo and can i use a normal light tester probe to find the ignition wire. Also if i want to wire couple of things to the ignition wire, do i use the same wire to connect all the products or is there another way of doing this.”

Personally, I would never wire anything off the ignition wire, it can mess things up (there are actually more than one wire which get power when you turn the ignition on.) If you do want to find one to use just for that little ignition wire on a modern fancy radio system, just take the plastic off the steering column to access the wires, and when you turn the key on, check them with a test light and when the light comes on, that’s got power. BUT, you really should wire other accessories directly off the battery positive post, using the correct gauge wire and correct fuse for whatever application you’re using. That way you won’t mess up the electrical system by hooking up something where it shouldn’t be (it can really open up a can of worms that you won’t like the results of.)