Review: 3M Scotchlok IDC Butt Connectors

Review: 3M Scotchlok IDC Butt Connectors



3M’s Scotchlok brand quick connectors are incredibly handy for loose wiring jobs. We tested their UY2 “butt” connectors, intended to join two conductors end-to-end, but the series also includes cap, tap, and even four-way connectors in various gauges.  To use, just insert the cut ends of the wires, aligning them with the internal metal slot terminals, and push down on the tab to make the connections. 3M only warrants their published specs when the deal is sealed using their specially-designed E9-Y hand crimping tool, but, between you and me, we had pretty good luck with regular pliers, too.  Much faster, better looking, and (we expect) more durable than wire nuts.

12 thoughts on “Review: 3M Scotchlok IDC Butt Connectors

  1. joe leier says:

    Properly used, wire nuts give a better connection. An electrical connection should be mechanically as well as electrically sound. Wire nuts should have the wires twisted together first, then the nut installed. The twist mechanically and electrically connects more surface area together, so less resistance at the connection, and the spring in the wire nut keeps the connection tight. A wire nut with silicone grease , will keep the moisture out as well. The 3m connectors are good, but they do not have as much surface area and therefore are not good for any good current carrying capacity. They are great for communications and low current devices. The wires can also be pulled out of these, so mechanically the cables should be secured to prevent the oops factor. I am not against these connectors as I use them for low current and communications connections, but I want to make sure people understand that wire nuts (when properly terminated) are more durable and their connections are more durable than the 3m connectors.

    1. joe leier says:

      I wanted to add, any trailer wiring that I have repaired always had the type of connectors that press down and pierce the insulation to make the connection. These always fail after a few years. A wire nut, or better yet a soldered connection seldom fails over the course of time.

  2. William Abernathy says:

    Another way to do the same job is with a “B connector” (Google it). B connectors do the same job (stripless crimp-splice of small insulated wires), offer as-good or better electrical and mechanical connection, and cost less. The reason the phone company preferred the IDC connectors long enough to make them a standard is that they have goo in them that makes them weather-resistant, and it’s easier to inspect (a squished IDC connector is visibly squished and you can see what the wires are up to inside the clear housing. B connectors are opaque). If weather-resistance is important, you can also get B connectors with insulative goo, and I think they still cost less than the IDCs. I have both, and use whichever is ready to hand, but prefer the simplicity of the B connector.

  3. rocketguy1701 says:

    While I wouldn’t use these for a serious power carry application, for general electronics, they are quite good. They also have a silicone gunk inside them for waterproofing that seems to work very well. If I was concerned about it getting pulled on, I would often twist the pair after crimping for mechanical strength. Pliers work okay, just try to make it as flat as you can.

    They’re quick, and better in damp environments than a standard wire nut. Of course soldered with heatshrink might win if it’s really sealed well, but these are more convenient. Always with the tradeoffs of course.

  4. Justin says:

    I’ve only seen these sold for reticulation solenoid connections which I think is all they are good for, as I usually have at least one dud connection everytime I use them. And they are expensive, but can be a good addition to your toolbox for those ‘get you out of trouble’ moments

  5. Andrew says:

    I’m a little concerned about comparing these butt connectors with wire nuts (marettes); they’re not designed for the same applications. Butt connectors are for low voltage multi-strand applications and are particularly well suited for mobile electronics where they can sustain vibration without coming apart, whereas wire nuts also known as Marettes, are for high voltage (120/240) single strand connections. Personally, I prefer barrel connectors like these (requires proper set of crimpers):

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Kelley Benck

Kelley Benck took the Project Make class at Analy High School in Sebastopol, Calif., and started interning last spring. She “was nervous about what sort of projects I would be asked to do, but those jitters were shaken away when I was handed the daunting Tesla Coil.” She hopes to design and 3D print a model 1966 Austin Healey.

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