We love creature comforts. Though we openly lament the complexity of our daily drivers we think nothing of heaping electrical devices on our fun cars. We'll go way out of our way to get power windows, power door locks, high-watt audio gear, climate control, high-powered lights, and electronic engine management.
Unfortunately, the effort we invest in electrical devices doesn't seem to extend to their installation. Generally speaking we mount electrical components well but we tend to drop the ball when it comes to integrating them with the rest of the electrical system. Most of us simply hard wire a device to the rest of the system and dread servicing the part or any other one near it. Because to remove a hard-wired electrical component means cutting its wires and that means having to reconnect wires likely made too short by the splicing junction. Creating joints with spades and push-on terminals seems like a good idea but a bunch of nearly identical-looking wires each equipped with the same type of terminal is a nightmare puzzle when working upside down and backward under a dark dash. That's no way to live.
Fortunately, it's not the only way to live either. As early as the '50s auto manufacturers began equipping electrical components with multi-terminal connectors or plugs. Need to service a device or get to one behind it? Just pull the plug and remove the part. And because of the plug's index only one-way reconnection happens just as effortlessly.
And that's really only the start. Because the OEMs used these multi-terminal connectors for decades they're considered service items. They're available just about everywhere and as a result they cost peanuts—new ones from the right sources cost so little that it's not even worth harvesting used pieces.
What follows is what you need to know about the three most popular connector styles: Packard 56, Weather Pack, and Metri Pack. There are others but since they lack the utility of these three we'll save them for another entry.
For now, though, learn what it takes to make a wiring installation as serviceable as the one in your new car. These connectors are so handy, affordable, and easy to use that you'll wonder how on earth you did without them so long.
The Packard 56 is the grandfather of the modular electrical connector. If the Packard name sounds familiar it's for good reason: the Packard brothers of automobile fame started it in 1890. In fact the Packard Electric Company bankrolled the Packard Motor Car Company nine years later.
In 1932 the brothers sold Packard Electric Company to General Motors who named it the Packard Electric Division. The company released its 56 series as an un-sealed modular system in the mid '50s. The 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, and, certainly most familiar, three-pin headlight plugs.
The Packard 56 terminals fold over the conductor to form a high-pressure crimp that seals the conductor strands as a soldered joint does yet achieves a superior electrical connection than solder can. The terminals also alleviate strain on the exposed conductor with a secondary crimp that grabs the wire jacket. All 56-series connectors use 1/4-inch blade-type terminals that can handle as much as 48 amps continuously. Though the terminals require a special crimp tool, popularity has made powerful ratcheting models refreshingly inexpensive.
Packard 56 connectors are small and unobtrusive. Since they date to the '50s they're historically possible on a period hot rod or custom (though unlikely at the time since the tools were once exceedingly expensive). The lack of sealing means they don't work well in damp locations, so keep them close 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 56 is handy for sure but it has one fatal flaw: it doesn't protect the terminals from oxidation. So in the '70s Packard Electrical Division created the Weather Pack (get it? Weather-resistant Packard).
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 inline exclusively and don't connect to a specific component as Packard 56 can. Furthermore, the seal system prohibits more than one wire from meeting a terminal.
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 is more than compensated for by availability: every parts store across the country has Weather Pack service parts. And they're almost insultingly inexpensive if you buy them right.
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. Though every Metri Pack series has a sealed version, some variants trade the sealing component for a smaller package size. Anyway, not every connector needs the sealing capacity.
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.
Metri Pack isn't a connector design as much as a group of connectors based on terminal width. The 150-series connectors feature 1.5mm terminals and handle 14 amps; 280-series connectors feature 2.8mm terminals and handle 30 amps; 480-series connectors feature 4.8mm terminals and handle 42 amps; and 630-series connectors feature 6.3mm terminals and handle 46 amps.
The series uses a separate clip that retains the terminals. This TPA, or Terminal Position Assurance, retains the terminal at pretty much all costs. In fact, it works so well that some terminals lack the locking tangs.
The 280-series Metri Pack is incredibly versatile. Its footprint not so coincidentally matches the blade spacing of many universal automotive components like mini automotive fuses (APM/ATM), relays, and flasher modules, making it perfect for universal applications. In fact General Motors designs its modern fuse/relay panels to use 280-series terminals pretty much exclusively, something that makes them readily adaptable to other applications. Coolest of all, even-numbered 280 electrical connectors can be used as inline fuse holders—caps for two- and six-cavity female connects exist for this specific purpose.
Though the same fuse-holding application holds true with the 630 series, the series is far larger and less versatile. Because it and the 150 series use a slightly different terminal attachment we're going to devote another story entirely to them and some other slick connectors.