DIY: How to solder your wiring connections like a professional


Last week, Hagerty’s Matt Lewis showed us the details of using crimp connectors to join two wires. Now, for our latest DIY video, he demonstrates the proper technique for using solder to join wires.

This is a companion discussion topic for the original entry at https://www.hagerty.com/articles-videos/articles/2018/08/08/diy-advanced-soldering


Found that when soldering it’s best to start with a clean soldering iron. I have also found that by placing a small amount of solder to the iron it makes a better thermal connection to the wire which makes the entire process faster. I


It takes much less time to make a proper soldered connection…than chasing down a poor, intermittent connection later. If you don’t have time to do it Right, when will you have time to do it Again?


I would like to know what type of solder to use for automotive use. There seem to be many types and thicknesses.


Rosin core for electrical work vs acid core. Many soldering kits include a sponge. Irregardless, get a small sponge and moist, not wet, while your iron heats up. Apply some solder to the hot iron so that the flux can clean it and then wipe it on the moist sponge occasionally as you work. Tinning the iron by putting a small bit of solder on it allows the heat to conduct into the work.


All ways clean your solder joints with alcohol to remove acid from the flux


When soldering to the terminals on a device like the switch shown in the video, it’s best to use a heat sink on the tabs to prevent damage from tod much heat transfer into the device, I have used small hemostats to accomplish that. They also will hold the device in a position to make it easier to be able use both hands to get the soldering done.
Just a thought from my many years


If I were attaching a wire to the switch terminal shown, I think I would crimp/solder the wire to the proper size spade connector and then simply slide it onto the terminal connection.


The Only way to go …
My Jeep hasn’t had a problem in 9 years after its original Resto !!
Great Video !


Although I don’t know a professional solderer, I have soldered tons of wires and thought I knew everything. I had not thought to solder in the middle of the wire by starting with wire strippers. Also, the video affirmed most of what i was doing but did give me a few subtle pointers as well. By the way, I am installing a FAST 2.0 fuel injection system. Nothing but crimped, unsoldered connectors. That must be why I must run power directly to the battery. Makes me wonder. Great videos, Matt!


I have used for many years rosin core solder. Thin for electical work on vehicles. I’ve used many soldering irons shown. The best seems to be the pencil tip of under 20 watts for most electical work on vehicles (bikes included). But most solder takes much longer to flow into the wires and as such transfers more heat into that circuit (wire) if existing to the vehicle. Instead I’ve found using low rosin core solder content best closer to silver solder and using flux paste with a brush onto the connector to be soldered. Once completed wipe off with a damp cloth and then heat shrink. I’ve even done this on crimp connectors to make a stronger connection. The flux paste makes heat up much less and so less heat soak into the existing wires (which in old cars is already brittle in some cases) and it keeps your hands from getting burned!!! Also if you have it places where moisture is a concern go one extra step and put some electrical grease on the connection before putting the heat shrink on…should keep moisture out for a long time!!!
Also if green corrosion on wires is found dip it into some baking soda first to get rid of that and use a wire wheel (dremel) to shine it up and tin before soldering. Wish some of the TOOLS of the trade used now were around and available when I started doing electrical on vehicles…or had the $ to afford them…good video Matt keep up the electrifying video’s!!!


I have always felt that good penetration is key for successful connections.


Agreed ,very clean no contaminating elements to interfere with the heat and penetration of the solder.