To keep things simple, we specified the two most popular styles of automotive solderless connectors in the automotive aftermarket: non-insulated and insulated closed-barrel terminals. While some technicians apply solder to the non-insulated variety as a sort of insurance policy, that's a subject beyond the scope of this article (see the soldering sidebar), and one that we may address in a future installment.
Instead of endorsing any one particular style, we present to you several for you to choose from. As you do, keep in mind the following: Those who create entire wiring harnesses on OEM-level machines for our industry use at least one of these methods and tools to successfully install wiring harnesses. If you follow their lead and invest the time and attention necessary to do any job correctly, you're likely to achieve similar success.
To Solder Or Not To Solder
If there's a single most contended subject in the crimping world, it's the solder debate. We'll let Wire 1's Ken Whitney land the first blow: "When using a quality tool and when done properly, a crimp is every bit as good as any soldered joint. The conductivity and strength are both great, and the crimped terminal is as strong as or stronger than the wire itself."
Then again, both American Autowire's Michael Manning and Haywire's Ken Logue endorse soldering the tip of a crimped terminal to ensure the integrity of the seal. While Painless Performance's Dennis Overholser agrees with that in theory, he noted that, in practice, the occasional electrician is more likely to overheat and damage the wire than create a good joint.
Affordable Street Rods' Rich Fox outright condemns the practice and offers examples of failed solder joints made by aftermarket vendors. In fact, governing bodies like the Federal Aviation Administration permit only crimped joints, for reasons such as Whitney noted: "They figure that you're more likely to create an effective crimped joint than a soldered joint."
Luckily, they all meet at middle ground, as summed up by Manning: "A mechanical bond, generally in the form of a crimp, is the basis of any effective terminal installation." For that reason we have concentrated specifically on how to affect a reliable crimp and left soldering for another day.
Unless they're on ground wires,...
Unless they're on ground wires, non-insulated terminals require external insulation. Polyolefin heat-shrink tubing is a standby since it's affordable, durable, and shrinks to half its diameter when heated. Choose tubing with a large enough inside diameter to slip over the terminal's barrel, and trim it about 1/8- to 3/16-inch longer than the barrel itself. It goes without saying that you'll have to slip this insulation over the wire before fastening the terminal, but we'll remind you anyway.
Each terminal style requires...
Each terminal style requires a dedicated tool, and each tool generally has multiple stations based on terminal size. So far we've worked with non-insulated terminals, which generally call for these dimple/cavity dies. While these antique Vaco 1900-series pliers (now Klein) feature a station for each terminal size, the Klein 1006 pliers Rich Fox uses have only one station set for 14- to 22-gauge (red and blue) terminals. To crimp 10- to 12-gauge terminals, he widens (not deepens) the cavity in a second set of pliers.
Always use the appropriate-gauge...
Always use the appropriate-gauge cutter on a dedicated wire-stripping tool to strip the insulation from a wire, as undersized cutters and improvised tools like knives, razors, or plain wire cutters will impair the wire's conductivity and longevity by gouging or eliminating the highly critical outermost wire strands. Dedicated pliers are investments; they fit in tight spaces and offer decades of reliable service. The ergonomic grips on Ideal's Kinetic Reflex wire strippers are easy on hands too.
According to Fox and Dennis...
According to Fox and Dennis Overholser, orient the barrel so the pocketed die cradles the barrel's seamed side and the dimpled die strikes the barrel's solid side. Slide the terminal over the conductor until its barrel abuts the insulation and squeeze the handles until the pliers close.
While official crimping literature...
While official crimping literature says to submit test crimps to a measured pull test, every wiring professional we spoke to noted that a good stiff tug on every crimped joint is good enough to ensure sufficient grip pressure. Technically, a crimped terminal should withstand 70 or more pounds, so don't be shy. If you can pull a crimped terminal from its wire with your bare hands, your tools, terminals, or methods need refinement. Nerve wracking? Yes, but wouldn't you rather find out now?
Insulated terminals create...
Insulated terminals create a few unique issues. First, their insulation collars make the terminal that much more pressure to crimp. Furthermore, the collars all but forbid visual inspections. Considering the risk of creating an ineffective crimp, ratcheting-handle crimpers like these from Wire 1 and Molex (Service Grade 64016-0036) are money well spent. When compared to pliers-style tools, their compound action generates greater crimp pressure for a given amount of hand force. More importantly, they don't release until the dies reach the optimum crimp height.