Fun day at work yesterday. We are going to display our trailer (a 44ft., three axle, fifth-wheel) at an expo on the East Coast. We did some modifications to the DC bus based on the reverse engineering and research I did. I generated schematics, too.
Yesterday, we sent our trailer off to an expo (personnel to follow later). The commercial tow vehicle we contracted was supposed to be already set up for us. Unfortunately, his electrician screwed up the harness and I had to rewire it. We plugged our trailer into the electrical socket but the test was a total failure. Turn signals activated the backup lights. There were no brake lights at all. I spent more than a hour rewiring his harness. A harness he paid US$250 for.
Doing some research on the internet, I found out that the commercial seven-pin connector does not have the same signals that we require on our seven-pin non-commercial connector. His provides no reverse lights and has a separate signal for the brake lights. Our non-commercial trailer makes use of both turn signals being on at the same time (and not blinking) to indicate brakes. I ran off to Radio Shack and bought out all their high-current diodes (2.5 Amp) and wired them between the turn signal pins and his brake signal. There is no way to account for reverse lights, but the big rigs don't have them anyway so it is a don't care.
Not to brag or stroke my ego, but no one here could have fixed that issue but me. Seriously. I just justified my existence within this company. The trailer could not have been hauled without the brake lights and we would have missed a tremendous opportunity.