1995 Ford Econoline E350 Horn Cigar not working

I have a 1995 Ford Econoline E350 motor home with a 460 engine. The horn and cigar lighter no longer work. The fuses are okay and the hot wire has power. I am looking for help to locate the grounding wires for this circuit as I believe that is my problem. Any help will be appreciated.

The power comes from the center of the outlet and the power wire connects to there. The ground then goes to the side of the outlet. Since I don't have that van to look at, here are possibles. That ground clip on the inside goes all the way through the outlet and touches the metal of the dash to complete the circuit, and that connection could be bad. That ground clip on the inside goes out and has a ground wire connected to it that goes to a ground point on the firewall, and that connection could be bad.

Thank you for the information you posted for me. I will start and troubleshoot later this week and let you know what I find. Take care Gordon