Peterbilt Switched CB Circuit?

I would check each fuse in the fuse block with a test lamp and see how many and what are switched.

 

No. You can go to the fuse box and find the cb radio fuse and pull it. then determine with is the radio side and which is the power side.Take about a 6" long piece of 14 gauge wire with a fuse in it (you can buy it this way at a autoparts store) pull the fuse out of the wire and insert the fuse from the fuse box that used to run the radio. Plug one end of that wire into a switched fuse (hot side) and the other into the radio side where you pulled the fuse in the fuse box.

Or ask your shop to do this for you. I used to build fire and police vehicles and this is exactly how I would have wired it any vehicle. Check with your shop and do not forget the fuse it is there to protect the truck not the radio. Always fuse everything you install. 3 to 6" and there should be a fuse.

 

In a previous life I had a radio shop where we built Police, Fire, etc.. Radios Light Bars, Sirens and we had to frequently set stuff up to happen when the operator of the vehicle would flip a certain switch. Glad to help.