QUOTE(Cap'n Krusty @ Jul 7 2009, 03:05 PM)
Soldering is NOT recommended for automotive wiring. Proper crimps using non-insulated connectors, then encased in shrink tubing where necessary, is what all the European manufacturers recommend. In fact, they specifically forbid soldering on newer cars. Insulated crimp connectors are just as bad as soldering.
The Cap'n
The problem with a soldered connection is vibration and the resultant localized stress to the wire at the wire terminal-to-wire interface that causes it to weaken and break off. Soldering does have redeeming value because it encapsulates the connection from contaminants including air, and makes a good electrical/physical connection, but when used at wire terminals that are fixed to components, with wire that vibrates, it also creates a point of weakness in the wiring from the vibration. The best hand-done wiring connection in an automotive environment or any environment with vibration is a solid mechanical crimp, well-crimped so that it keeps all air and corrosion out of the interface and then strain relief bridging the interface usually in the form of heat shrink tubing to minimize wire movement relative to the wire terminal.
Even better are todays factory-molded connections where the wire gets its strain relief from a molded enclosure that completely protects the wire-to-terminal connection and inherently provides strain relief. But outside of the factory, that type of conenction is not possible without special equipment.
I have no concern with solder-splicing 2 wires together when in a continuous run, even when vibrating, and protected by heat shrink, because one side of that connection is not fixed to equipment, both are free to vibrate the same. Even so, sometimes soldering to a fixed connection is not avoidable, and the only risk is that the connection may need to be redone once in awhile.