I have an old HU that I left a cd in. Can I just figure out which is +12 and GND for the HU and apply +12vdc to get the cd out?

Or do I have to pull out the other HU and replugin this one?

 

you should be able to put the constant and switched 12v together on a positive post of a battery or a hot wire and ground it and get it out with no problem.

 

as long as you have the HU harness plugged into the back of the old one. if you don't, you can look at another similar HU to get the wire pin locations of the 12V+/ignition/ground. if not, you'll have to unplug your new one and plug in your old one. this will work only if your new HU is from the same manufacture and is a similar model. good luck :thumbup: