Thanks for all of the assistance. I finally had time (and help) to climb under the trailer while getting brakes pressed etc. Now, I am more confused about some things and knowledgeable about others...
Here is what I found:
When the truck is not running I have these voltages at the plug at the rear of the truck:
2 Blue 4.52 - trailer brake
3 Brown 11.73 - running lights
4 Black 11.73 - 12v power
5 Yellow .07 - Lt turn & brake
6 Green .07 - Rt turn & brake
7 Purple .01 - Back up lights
Then I attached the plug from my trailer and engaged the "emergency" stop button on the brake controller. I climbed under the trailer and opened the junction and tested the wires from there. Here is what I got:
2 Blue 0.00 - Brake controller (NOT GOOD)
3 Brown 0.22 - running lights (they were all on though)
4 Black 13.38
5 Yellow 0.01 - nothing connected to it from the trailer
6 Green 12.96
After I saw that #2 was at 0.00, I re-tested the voltage at the receptacle at the back of my truck with the "emergency" button depressed on the brake controller. It read the same as before, 4.5... I don't know if the brake controller functions when the plug is disconnected though. I know the "connection" light on the controller goes out so it probably doesn't have any effect without the plug inserted.
I am a litle concerned about the truck wiring because I remembered that a chipmunk had chewed a lot of wires in my fuse box last summer. A mechanic fixed everything and I haven't had any problems. I can't remember if we pulled the trailer since then or not. Maybe something got missed...
Hopefully, someone can make sense of my numbers and give me some ideas. I find it hard to believe that only the blue wire in that big package of wires is bad. Maybe it is though...
I also determined my "break-away" switch is junk! The contacts were bad before. I cleaned them up and got it working. Then I replaced the plastic plug. When I tested voltages later the plastic plug would NOT come out. It broke and now I have to replace the switch....
Thanks for any help!
2016 Puma 30RLIS
2011 Catalina 19RD - totalled by hail