2008 chevy 3500 accessory wire

Anyone know where I can find a 12V accessory wire in the 2008 Chevy 3500 truck?  Wire colors?

Most of the fuses in the dash fuse-panel are constant 12V, and those that aren't are keyed, so I can't figure out how to wire the radio to remain on in the accessory position and shut off when the key is removed.

Also, anyone know whether the wire colors for all airbags are common, or are they different for each year model?

Thanks.

Those rigs have retained accesory power factory.

What are you trying to do, that's not already done?

I have to install a two-way radio and the client wants it to be on the accessory wire so he can monitor the radio without the truck running.

I have probed every wire I can reach under the dash, and all of them are either constant 12V or only powered when the truck is running.

Any suggestions?

Thanks.

I know that on the 07s There is a wire on the ignition switch, that goes 12 volt when the key is in the on position.  The only problem is that it does not provide enough current to power anything.  But you can use the wire to trigger a transistor to trigger a relay.  I will draw you a diagram this evening, meanwhile if you can get by a RadioShack store and purchase a TIP41 transistor you will be ready when I get you the diagram.  We use this circuit when addidng XM to the factory deck.  There is no accessory position on the key.  His ignition will be on while radio is on.  Truck won't have to be running but ignition will be on.      Until the diagram, Base of the transistor connects to the 12v wire at ignition switch.    Collector of transistor needs a constant 12volt, fused at 3 amps.   Emitter of transistor is the positive output to terminal 86 of a relay.   Ground terminal 85 of the relay.   terminal 30 needs a constant 12 volts fused at 10 amps.  terminal 87 is the power wire for your 2 way radio.   With transistor setting on a table, the legs pointing towards you, and writing facing up.  The leg order from left to right is  Base Collector Emitter.   The metal tab of the transistor will have 12 volts on it.  You will need to insulate it somehow.  3/8 inch heat shrink tubing should fit over it.

Let me know if you still need the picture.

When you find the wire in the ignition switch, DO NOT try to connect the radio to it.  IT will not like it.

Nope the 42 is a PNP transistor.  You need an NPN.   I just noticed that RadioShack no longer sells the TIP41.   The TIP3055 will be the better, if they do not have that one near you the TIP31 will work.    They do sell these.  Sorry for the bad info.

Do you understand the connection instructions?        I can draw a pic if needed.  I have digital crayons.