A Crimp In Time Saves Nine
How To Properly Crimp Closed-Barrel Terminals
From the February, 2009 issue of Rod & Custom
All contributors: Chris Shelton
The last generation did more for aftermarket wiring than any that preceded it. While even the most serious do-it-yourselfer once clutched at the prospect of installing something as simple as power windows a mere decade ago, just about all of us can wire an entire car nowadays due to well-designed kits, comprehensive instructions, and precious technical assistance.
While the way we install our wires has improved by leaps and bounds, the same can't be said of the way we end them. All too often an enthusiast will tediously route and bundle a whole harness and simply kludge the terminals with poor-quality tools or the wrong tools altogether. Making matters worse, a poorly installed terminal, much like many a poorly welded joint, doesn't necessarily look shabby.
That's a potentially fatal pitfall since most electrical problems start at wire tips well hidden by the terminal itself. Above and beyond connecting the terminal to the wire and conducting electricity, the terminal installation must effectively seal the end of the wire. If it doesn't, oxidizing elements like the air around us will wick along the wire strands inside the terminal and corrode the wire well under the insulation. In the best-case scenario, a poorly installed terminal will eventually work intermittently or stop working altogether. On the other hand, since corrosion increases electrical resistance, resistance increases heat, and heat induces more resistance, a damaged wire can slip into a destructive cycle and fail with catastrophic (and blazing) results.
Automotive manufacturers over the past 50-odd years have consistently created effective and airtight terminal installations by crimping or deforming terminals' barrels to capture the wire strands. If there's a detractor to this process, it's that OEM-grade tools are incredibly expensive and require frequent calibration. Furthermore, OEMs use a type of terminal variety that is often pretty hard to find. While non-OEM-grade tools and consumer-grade terminals have been available to enthusiasts for some time, a lot of them-particularly the cheap ones-don't do a very effective job. Crimping has earned a pretty bad reputation as a result of failures due to inadequate tooling, chintzy terminals, or poor education. Making matters worse, just about all poor-quality tools and terminals are still available at even reputable auto-parts stores, perennially leading would-be electricians to failure.
Luckily for us, more and more specialty tool manufacturers and vendors like Molex, Klein Tools, Wire 1, and Snap-On offer high-quality electrical tools that bridge the gap between expensive OEM-grade and dime store-quality tools. While these tools cannot be considered OEM-grade since they don't feature the approved calibration mechanisms for mass production, Molex's Bob Grenke assured us that such exacting controls are of little consequence since we enthusiasts and professionals can take the extra time to verify a crimp's quality. He adds that most of these tools are fully capable of creating thousands of effective crimps over their lifespan if cared for properly.
To find the proper way to use these tools, we asked a few wiring specialists to tell us their own definitive way to fasten a common closed-barrel terminal to the end of a wire. Since we have a collection of professional opinions, this is the point where things potentially get sketchy. Naturally there are multiple schools of thought, and each one has its merit; however, some philosophies seem to contradict others.
The terminal's barrel is the...
The terminal's barrel is the section that actually meets the conductor material and is the area within the sleeves on insulated terminals. There are three basic barrel dimensions based on wire gauge, each with its own corresponding color. From left to right, they're 10- to 12-gauge (yellow); 14- to 16-gauge (blue); and 18- to 22-gauge (red). According to every technician we talked to, always choose a terminal barrel size range to match the wire gauge; an improperly sized barrel will prevent the essential wire seal and will likely fail.
All terminals feature a seam...
All terminals feature a seam (shown here), a result of the manufacturing process. If given the choice, Ken Whitney said to pay the modest premium for brazed-seam terminals since they maintain their integrity under crimping pressure. Furthermore, personal experience proves that thicker barrel walls retain their crimp better. Here's a tip: While some owner/operator parts stores may or may not offer premium-quality terminals, assure yourself that franchise stores and discount tool outlets most likely do not (based on more personal experience). If at all possible, buy from a dedicated electronics vendor.
Strip enough insulation so...
Strip enough insulation so the exposed conductor material matches the barrel's length and the insulation abuts the barrel. While most terminals feature a tang at the end of the barrel that prevents the conductor from interfering with the business end of the terminal, some don't. In such cases, trim the exposed conductor flush with the barrel's end or let it exceed the barrel by about the conductor's diameter.
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.
Upon proving the quality of...
Upon proving the quality of your crimps, slide the shrink wrap back over the terminal's barrel and apply heat. Probably the most reliable source is a heat gun; however, heat from a butane lighter or a propane torch works just as well. Make sure to use only the heat, and not the flame itself. For what it's worth, adhesive-lined tubing very effectively seals the joint from moisture.
Due to their greater crimp...
Due to their greater crimp pressure capacity, ratchet-style dies often feature wider jaw contact area than pliers-type tools. Furthermore, each station in most ratchet-style dies also features a secondary station with rounded jaws. They crimp the extended barrels exclusive to double-crimp terminals.
Insulated-barrel terminals operate on the same crimping principle as their bare brethren, but the tooling differs. In this case, they rely on pliers with shallower jaws, similar to those on this Molex pliers-style multi-function tool. While these simple pliers will get the job done in a pinch, they're not necessarily the tool you'd reach for to wire a whole car.
Most people refer to double-crimp...
Most people refer to double-crimp terminals as strain-relief terminals, since their secondary larger barrel crimps to the wire's insulation, thereby relieving the strain on the unsupported conductor. From left to right are a standard vinyl-insulated terminal, a double-crimp terminal with its nylon insulation intact, and a similar terminal stripped of its insulation. Ken Whitney suggested we pay the small premium for nylon-insulated terminals; nylon resists higher temperatures and doesn't become brittle, as PVC (vinyl) insulation often does.
Once again, give the terminal...
Once again, give the terminal a good tug to verify its installation. For what it's worth, this editor never considered using insulated terminals in the past specifically because ordinary pliers-type tools generated unreliable crimps despite the wrist-damaging hand pressure they require. Suffice it to say, shop time spent with a ratcheting crimp tool changed that.
Orient the terminal over the...
Orient the terminal over the stripped wire (same method as described earlier) so either of the die's jaws squarely strikes the seamed side of the barrel. If using a ratchet-style tool with secondary crimping pockets, make sure the primary jaws, or the flatter of the two sets, generate the actual crimp close to the terminal's working end. In such cases, ensure that the secondary jaws crimp the remainder of the barrel.