Soldering is an important step. In our How to Solder page, we highlight a couple things. Most important is not to hold the iron for too long on the plug. The housing melts at a lower temperature than the soldering iron. But by holding the iron on the solder for just a few seconds, the solder melts with the heat going through the wire strands and onto the plug itself. Remember let to hold the plug and wire steady once the iron is removed. We have seen cold solder joints form that increase resistance in the line.
Another impact of holding the iron on too long, is that the solder can wick along the strands under the insulation. This creates a stiffness that is not needed. It is better to keep the solder at the contact area purely for the joining.
If the iron heats up the housing, it can change the shape of the plug location. That said, we do not recommend connecting the other plug end while soldering. The plugs are engineered to create a solid contact.
Here is an example of a before and after of a solder done on a plane of a flyer at our local airfield. We are glad he has a solid connection now, and no worries about losing electrical contact in flight.
