If you’ve worked on any General Motors vehicle from the recent past you’ve encountered one of the greatest innovations to the automotive industry: the electrical connector. Prior to the design—which actually dates to 1955—screws fastened wires’ ring terminals to electrical components. More than cumbersome and time consuming, the spaghetti system opened the door to improper connections that could easily fry a component, wire, or in the worst cases, the whole system.
GM owes the design to its Packard Electrical Division (yes, the same Packard as the auto maker—GM bought the company’s electrical division in 1932). That 1955 design consisted of simple nylon-bodied male and female connectors that fit only one way. So reliable and user-friendly was this system that it lasted well into the 1970s. During the decades that followed, GM introduced new designs that sealed the connections from the atmosphere, shrank the package size, and increased the connectors’ current capacity. Other manufacturers followed with connector designs of their own and now it’s plain impossible to work on any car without encountering electrical connectors.
So what’s the cost penalty for such versatile components? Believe it or not; very little. Sure you could harvest connector bodies from boneyard vehicles, but why bother when new ones made by Delphi (Packard Electric Divison’s name) can cost as little as 18 cents. Yes, 18 cents. Most run in the 50-75-cent range, and the most expensive common ones run between $1-2.
The terminals are similarly inexpensive but most shops require minimum orders of 50 to 100. But at 10-15 cents apiece, a pack of 50 costs about as much as a pack of 5-10 at automotive parts stores.
If there’s anything truly wrong with the designs, it’s information and tools, specifically the lack of them. Without those, these connector systems can be a real burden. In fact, it’s impossible to work with connectors without the right goods.
The single greatest expense is the tools, but they’ve come down radically over the past generation. At one point, only Packard offered crimping tools and they’d often run as much as $750. Nowadays, even Packard crimping tools run $75 to $175, but they’re wholly unnecessary unless you’re a pro (in which case you’re reading this to find faults). I found great success by modifying $40 open-barrel ratcheting pliers (Del City, PN 990168) to crimp Packard 56 terminals (explained in the captions). I use $30 crimping pliers (Del City, PN 990174) to crimp Weather Pack and Metri Pack 150 and 280.
Actually, I hung up the pliers for Weather/Metri Pack. Not too long ago Petronix, the company that makes those handy electronic-ignition retrofit kits, introduced high-quality modular ratcheting crimp pliers. Modular in this case means replaceable die sets that let these pliers crimp a pretty broad array of terminals. The various dies don’t do Packard 56, but one does insulated terminals properly (unlike the stamped pliers); another, non-insulated closed-barrel terminals; another for open-barrel (F-type) terminals like you’ll find in standard relay plugs; and yet another for spark-plug wire terminals (which work far better than the hokey stamped pliers). But most importantly, a set of recently released dies crimp Weather/Metri Pack in one operation (whereas it takes two operations with my old tool).
Things that do everything usually don’t do anything well, but these hold a lot of promise. The pliers themselves largely resemble my ratcheting crimp pliers and those things have lasted a decade and at least half as many complete wiring jobs. Those are just as tight as they were when new, which gives me faith that these will live up to my expectations. These connectors are useful well beyond their ordained OEM applications. The right ones can make any aftermarket wiring harness feel and come apart just like an OEM one. They make accessories wonderful to install and service. Just knowing how to disassemble and assemble these connectors makes it far easier to strip engine harnesses for new installations.
What follows are the tools, tricks, and general information regarding the three most popular systems: Packard 56, the waterproof Weather Pack, and its more sophisticated brother Metri Pack (see the Packard theme here?).
So read on and learn what it takes to make a wiring installation as serviceable as the one in your new car. So handy, affordable, and easy to use are these connectors that you’ll wonder why you cursed them for so long.
Packard 56
These housings come in a variety of configurations from plain inline connectors to specialty connectors that correspond to various devices like sending units, flasher modules, ignition switches, alternator plugs, dimmer switches, and certainly most familiar, three-pin headlight plugs.
The terminals resemble those for Bosch-style relays in that one set of ears fold over the conductor and another over the jacket to affect a strain relief. For those who don’t trust crimped connections, lay your fears to rest. When done properly, they achieve better conductivity than a soldered connection (lead and zinc aren’t as efficient as brass but a crimp is direct) without the risk of overheating and crystallizing the conductor. The OEMs haven’t soldered things in decades and the FAA bans it in all but a few specialized applications.
All 56-series connectors use 1/4-inch blade-type terminals that can handle as much as 48 continuous amps yet are small and unobtrusive. The lack of sealing means they don’t work well in damp locations, so keep them to the engine compartment or interior. And they can be a real bear to connect and pull apart, especially when cold or in tight confines.
Packard Electrical Division made dozens if not hundreds of 56-series configurations. Shown here are one-cavity connectors, a stacked three-cavity connector, and a really handy flasher-module connector.
The female Packard 56 connector resembles a plain push-on terminal. The foreground female terminal shows the “wings” that fold over the conductor and jacket. The middle terminal shows the tang that locks the terminal into its connector. The background terminal is the male.
Ratcheting crimpers use compound leverage to affect a crimp far stronger than any stamped pliers can, necessary because the 56 terminals are thick. Their pawl won’t release until they achieve a complete crimp. Del City stocks one that can be modified for 56, PN 990168.
Purpose-made 56-series crimpers are rare and expensive when you find them. The PN 990168 crimp pliers officially crimp lighter terminals like those in relay sockets or pin-type connectors (like Molex), which have a shorter distance between the locating “wings.” But the dies can be ground for clearance as shown here. Not difficult work.
I find it easiest to set the terminal in the dies and then insert the wire, but it doesn’t photograph well. Strip approximately 3/16 inch of jacket to expose the conductor and push it in the trough until the jacket bottoms on the primary crimp ears as shown here.
Once the wire fits properly in the terminal, squeeze the crimp-pliers’ handles until the tool fully closes and releases. Even with the compound leverage, it takes a fair bit of pressure to affect a solid crimp. A proper crimp folds the tangs over the conductor and the insulation as shown here.
The terminals correspond with the connector gender: male with male and female with female. Tangs lock the terminals into their respective connectors. The tangs on the female terminals orient to the connector’s notched side (shown here) but the male has no orientation.
It takes a small, flat-bladed tool to release a Packard 56 terminal from its connector. The correct one has a blue handle, but I make do with the smaller red one. It pushes in the groove for the female connector. Initially push on the wire as the tool goes in then pull when the tool seats.
The same release tool or even a small screwdriver blade presses against the side of the blade tang to release the terminal.
Connectors can make a harness come apart anywhere. It can also make a non-plug component removable as seen here. It’s seriously nicer than making individual connections.
Weather Pack
The Packard 56 is handy for sure, but it has one fatal flaw: it doesn’t protect the terminals from oxidation. So in the 1970’s, Packard Electrical Division created the Weather Pack – a connector system that, as the name implies, resists water and oxygen. Packard/Delphi’s sealed system uses two silicone seals, a large one on one connector body and small round ones where each wire enters the stations in each body. Like the 56 series, a pair of ears on the terminal fastens to the conductor. But in Weather/Metri pack, a second pair of larger ears fastens the small round grommets to the backside of the terminal.
Though Weather Pack is a modular system, it achieved its weather resistance by sacrificing some of its utility. For the most part, Weather Pack connectors are mostly exclusive to harnesses and connect to specific components in only a few applications, like the square, four-cavity plug on a 700-R4 transmission. The seal system also prohibits more than one wire from meeting a terminal. If you need to gang a pair of wires, you’ll have to do that outside the connector body.
Weather Pack’s relatively small surface-contact area limits constant current capacity to 20 amps, less than half the capacity of Packard 56. But the design more than compensates for availability. Every parts store across the country has Weather Pack service parts, and they’re almost insultingly inexpensive if you buy them right.
Weather Pack connectors are available in seven configurations: from one to six cavities in a flat format and with four or five cavities in a stacked format (four for the 700-R4). Shown here are a two cavity and broad six-cavity connector. Each set consists of a tower (halves with green seals) and shrouds (no seals).
Here are male (foreground) and female Weather Pack terminals. The terminal selection in Weather Pack is pretty limited due to its relatively limited current capacity. Two sizes are available: one labeled 15 for 14-16-gauge wire and another labeled 20 for 18-22-gauge wire.
Weather Pack achieves its weather resistance with silicone seals on the towers and by these small silicone seals that slip over the wire insulation. They’re available in several sizes, but due to the relatively limited wire-gauge range, gray (14-16 gauge) and green (18-22 gauge) are the standards.
Slip a silicone seal over the wire with the fat side away from the terminal and push it back sufficiently to clear the terminal ears. Then strip approximately 3/16-inch of the jacket and push the wire into the terminal until the jacket edge catches the ears. Seal unused cavities with a cavity plug (not shown; Packard PN 12059168).
Weather Pack uses an open-barrel design that uses special pliers. I abandoned my simpler tool for the modular system that PerTronix offers. It has removable dies, each of which crimps one of several terminal types. Like the blue-handled ones, these are compound levers that don’t release until they achieve a complete crimp.
The primary advantage of these dies is their ability to crimp the conductor and the seal in one operation. It’s probably easiest to insert the terminal first then push the wire/seal into it.
Weather Pack terminals technically aren’t gender specific; however, the tower (shown) best supports the female terminal and guides the male terminal into it. Open the hinged clip and push the terminal in until the tang clicks behind the ear.
Once the terminals seat in their respective tower or shroud, simply fold over the retaining clip. The connectors are fully ready to use at this time.
To disassemble Weather Pack connectors, first undo the retaining clip. The Weather Pack release tool is little more than a thin-wall tube in a screwdriver handle. Simply push over the terminal while pushing on its respective wire until the tool bottoms. Then pull on the wire.
Metri Pack
Metri-Pack represents Packard’s second-generation modular connector. The company completely revised the terminal shape to flat blades and rectangular slots and standardized it to a metric format, hence the Metri part in the name.
Metri Pack consists of four common series: 150, 280, 480, and 630. The numbers correspond with the blade width: 1.5 mm, 2.8 mm, 4.8 mm, and 6.3 mm. Naturally, the widths correspond to amperage capacity: 14 amps, 30 amps, 42 amps, and 46 amps, respectively. Most applications call for 150 and 280, but the information applies to 480 and 630.
Metri Pack also comes in a sealed and non-sealed version. The sealed versions use the same seals as Weather Pack. However, unlike Weather Pack, the terminals in the sealed system don’t lock in with tabs. Nor do they have a clip that covers the wires where they emerge from each connector. Instead, Metri Pack uses a separate plastic clip that fits in the backside of each terminal. Dubbed Terminal Position Assurance, or TPA, this clip system keeps the terminals in place by pushing against the silicone seals. Each connector subseries in Metri Pack requires its own TPA and the clips vary by cavity count. Yeah, it’s more parts to stock, but the system really works.
The non-sealed Metri Pack series doesn’t use the TPA system. Instead, each terminal has a tang that locks into the connector a lot like how Weather Pack does. Not every connector needs the sealing capacity but it’s probably more convenient and affordable to stock all sealed-type components than sealed and non-sealed. Anyway, the sealed and non-sealed connectors from a specific series plug into each other. About the only thing you’d need in non-sealed are terminals to plug into fuse panels. More on that in a minute.
Like Packard 56, Metri Pack is available in more applications than inline. In fact, pretty much all GM electrical components from the ’90s onward feature Metri Pack connections.
A few of the Metri Pack connectors have a little secret. The 280- and 630 series correspond with ATM (mini) and ATO/ATC fuse-blade width. What’s more, Delphi developed a whole series of components to correspond with that standard. You’ve seen them if you’ve taken apart a modern GM car: the little blades on flasher modules and relays among other devices just happen to match the dimensions on an ATM fuse.
It’s beyond the scope of this article but there are stand-alone, modular fuse holders and panels that use the Metri-Pack 280-series terminals. Maybe we’ll show those in the future. We’ll show you what they look like at the end, though.
The Metri Pack 280 bears a passing resemblance to the Weather Pack. These are the components of a two-cavity connector.
The 280 comes in several gauges. The common ones being 10-12, 14-16, and 18-22. Non-sealed 280 terminals (background) don’t use seals but will work in sealed connector bodies. The non-sealed ones crimp like a Packard 56; the sealed ones crimp by the Weather Pack method. Again, seal the unused cavities with the Packard PN 12010300 cavity plug.
As with Weather Pack, the non-sealed 280 terminals lock into their connectors with a tang. It takes a small release tool much like Packard 56 to remove the latter. This red one is for really small Micro Pack 150s but it works on 280.
The TPA clip pushes against the terminal’s seal making Metri Pack really durable. The TPA clips on either way and removes with a flat-head screwdriver or even a release tool. It also reveals the cavity letters (A, B, C, and so on) regardless of its orientation.
The two- and six-cavity 280 female bodies double as a fully sealed inline fuse holder. This shows the cap for the two-cavity female connector. It can mount with a #10 screw, but an optional clip is available. The same holds for the 630 series.
Remember the thing about the stand-alone fuse blocks? Littelfuse makes these 18-way (shown) and 60-way Mini Power-Distribution Modules (PDM). They hold 9 and 30 mini fuses, respectively. Even slicker, they’ll hold a combination of three fuses and three 280-format components like relays. Since all GM vehicles use that format, every parts store carries replacement parts. They come as components but a complete 18-way PDM costs about $10 and the 60-way sells for about $20. If equipped correctly, the 60-way could serve as an entire fuse panel.
