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Soldering Bullet Connectors

September 23, 2010 | Troubleshooting & Repair

By Bruce Tews

#1 – Cleaning the soldering gun

#2 – Splashing old solder from the bullet

#3 Tinning the cleaned gun tip

#4 Tinning wire before placing the bullet

#5 Heating the bullet before applying solder

Use a soldering gun if possible. High heat for a short time is better than low heat for a long time. Always clean the soldering tip with a damp paper towel before every de-soldering or soldering attempt! (photo #1) And, as always, wear eye protection!

If using a used bullet connector still attached to a wire, heat the bullet and pull it off with a needle nose pliers. To clean an old bullet, hold it in a needle nose pliers by the bullet's sides with the big hole facing down. Heat it with a soldering gun, and, when hot, bang the pliers on a hard surface without allowing the bullet to hit anything. Solder will spatter out (photo #2) and the inside of the connector will be clean and nicely tinned. You may need to do this more than once. If some old solder or small wire pieces stubbornly remain in the bullet, turn the bullet so the big hole is up, heat it, and put some new solder inside the bullet. Then repeat the heating and banging process. The small hole at the top must be open, and look almost like a new bullet connector. Don't do this in the kitchen since there is probably lead in the solder and it is toxic! If using a new bullet connector, no tinning of the connector is necessary.

Now, take the wire to be connected to the bullet and cut the insulation about 1/4 inch from the end. If the wire is corroded, try to strip it more until you find nice, shiny wire. If you do not have wire to waste due to needing the whole length of the wire, use a Scotch Brite pad to clean the wire, or some chemical. If using acid, make sure to thoroughly wash the wire after cleaning or it will retain the acid and may be a problem later in life. I am sure other folks on the list will have their special cleaning methods which we would love to hear about. Once the wire is clean, gently twist the exposed wire with your fingers and make a nice, straight end so all the wire is gathered with no little strands hanging out from the sides of the wire.

After tinning the gun tip (photo #3), nicely tin the wire with some rosin core solder (photo #4) and make sure no excess solder exists. Insert the wire into the cleaned or new bullet connector so that some of the tinned wire protrudes through the small hole in the bullet. If the wire is one of the thicker wires, you may need to diagonally cut some of the wire away from the tip of the wire to create a point that will fit slightly through the small hole of the bullet connector. Please note the some wire MUST protrude through the small hole.

Let gravity be your friend, and hold the wire's insulation with a 'third hand' an inch or two from the bottom of the bullet connector so the wire extending through the bullet connector is at the highest point for a thicker wire, or at a slight angle for thinner wires to help keep all the wire's insulation from going into the bullet connector. Note that most of the thinner original wires I have seen have the wire's insulation slightly inside the bullet, but not all the way to the small hole in the end of the bullet. With practice, you should be able to duplicate this, and not melt the wire's insulation when soldering. If you need to replace a bullet connector for wiring under the dash or in other cramped places, you can usually just bend the wire so the end is nearly vertical, and let the stiffness of the wire be your third hand.

Now, heat only a side of the bullet connector (photo #5), and when hot, use a little more solder on the exposed wire sticking through the small hole in the bullet connector. The solder will be sucked into the bullet connector. Remove the soldering gun tip from the bullet connector, and ensure the wire is very still until the solder hardens. The solder should be very shiny, and no solder should be on the sides of the bullet connector. If the solder is dull, you may have a cold solder joint due to the solder fracturing or dirt. If so, make sure things are clean, and redo the heat and keep the wire still again.

When totally cool, try to pull off the bullet connector with your fingers. It should not budge. Now, use a diagonal pliers and clip the any exposed wire from the end of the connector very close to the tip of the bullet connector. Now you should have very happy wiring.