Given that I already knew about two problems in the wiring harness that came with the avionics, and that it would be much more difficult to fix problems after the harness was installed in the aircraft, I decided to do a complete check of the wiring harness now. So I spent several hours today with an ohmmeter and the various installation manuals checking which pins on which connectors were connected together. In the end I found four pairs of pins (eight wires total) that need to be swapped in the intercom harness. The pairs of pins should be easy to swap once I purchase a tool to extract pins from Molex connectors. I also have to short two pins together to fix the last problem - I still have to sort out how I am going to do that.

I'm not happy with the problems in the wiring harness, but I am glad I found them now rather than later. This problem is much easier to deal with sitting in a comfortable chair working at the work bench than it would be if I was reaching in from the front baggage up behind the instrument panel.