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Wire Nuts vs. Crimp Connectors

It seems to me that nobody ever uses wire nuts when wiring up automotive electronical components. What is the advantage of the crimp connectors? I bought some to play around with, but I don’t really know how to crimp. Is there a special technique?

If you use crimp connectors you need crimp pliers.

Wire nuts are used where there’s high voltage applications. Mostly AC circuits. These circuits can handle a small voltage drop. When wire nuts are used in a low voltage application, such as a 12 VDC circuit found in vehicles, it can cause a voltage drop because of a poor connection. And this can cause a problem in the vehicles electricals.

Crimp connectors work, but it’s better to solder the connection and then use a heat shrink tape to seal the connection on automotive applications.


I used wire nuts to install an ignition switch from a junk yard on the 87 Mazda. I had a lot of extra wire, so it was easy. Then I tape over them and force the whole mass of wiring back over the cover. It worked great. I just don’t like the crimp connectors that much. Don’t really like wires either, for that matter.

Wire nuts are fine if you are using them where it is always dry - which does not describe a car.

The proper way to do this is to use crimped or soldered connections and use shrink tubing or electrical tape to seal the joint. Afterall, a fire in a car can be a pretty dangerous thing!

I think another concern with wire nuts in the automobile environment would be vibration.

(Tester says you need crimp pliers. That’s certainly the best way to do it, but sometimes you can get away with using heavy “regular” pliers or channel lock pliers or Vice-grips ™.)

That makes sense. Thanks, Tester.

Great advice. I have done quite a number of crimp connectors on quite a number of things, and they are not as reliable as a soldered connection in my book.

Haven’t you noticed that wire nuts get used with solid core wire and crimp connectors with stranded wire?

Best wire crimp tools are made by a company called “Betts” there are dozens of crimp tools that are not worth squat.

Crimp connetors were used exclusively in repairing aircraft wiring as solder joints present a fatigue point. You can bet we used connectors that were environmentaly sealed at the ends and please use the right crimp tool.

I also vote against wire nuts for vibration and wire strandedness reasons. In addition to crimped connections, I saw some connectors at Home Depot that might be of interest. They were basically heat-shrink connectors but with a glob of solder at the center. You stick in your wires and apply a heat gun. The heat gun melts the solder and shrinks the tubing in one step.

For a car stereo I say go ahead and use crimp connectors, but if working in the engine compartment SOLDER. Crimping under the hood at my place of employment could cause unemployment.

Crimps can be very reliable. All of the factory wiring connections (including under the hood) on most if not all cars are crimped. However, there is a big difference. The factory crimps were crimped using expensive automated equipment and skilled workers.
You can do just about as well with some training and practice using really good hand tools. Unfortunately, most of the hand tools available are crap. I fully agree that soldering is the way to go if you don’t have good crimp tools and experience.

Crimps are FAA aproved for aircraft but not good enough for under the hood work?wrong.A solder joint will be just the place a wire breaks when fatigued.

For perspective, you need a license that shows competancy in areas involving public health for a Taco stand, you don’t need a license for anything but making sure you pay your taxes for a stero joint.

Wirenuts are easy to find, require no special equipment, are OK to use in a dry enviromnent and also in a vibrating situation if they are also taped. Wirenuts are suitable for solid or stranded wire.

I have used soldered connections with stranded wire to advantage in a vibrating and/or flexing situation. The plastic sleeve included with a crimp connector provides a gradual flexing transition from the crimp to a wire and a soldered connection does this also where the wicking of the solder on a stranded wire decreases to none.

Crimping tools in a critical situation need to go through a periodic calibration/check process as do measuring instruments such as voltmeters, micrometers etc. Crimping with a tool other than the intended, suitable tool is possible but is a little risky.

The parts houses have begun to stock some of the better quality tools but they are expensive. The tool packaged with an assortment of connectors is somewhat of a joke. If properly installed with adequate heat shrink used the crimp connections appear to last indefinitely. It was my observation that wire nuts were for insulating single strand wires that were tightly twisted together prior to capping them.

There is no calibration/adjustment possible with my Betts crimp tool, it is all in the hand. It was not me that wrote the rule about no soldered wire repairs on aircraft, it was the FAA. The only people that use wire nuts on automotive electrical systems are hacks.

I agree, where I work, solder cannot be used to make any mechanical connection. Even if you were to twist the wires together, solder is not allowed. You must crimp connections subject to mechanical stress and vibration.

Our crimping tools are periodically inspected and qualified. They perform crimps and visually inspect before performing pull tests to insure proper crimping. These tools start at around $300 each.

Wire nuts in a car? Nope. I hate those cheap IDC connectors they sell for tapping into circuits too. Fixed too many of those done improperly that failed.

I cringe when I see someone poke their meter tip through the wire insulation too. Isn’t proper back probing of connectors taught anymore?

Heh. I think I have one of the “not worth squat” ones. That could explain why it’s so hard to strip a wire as well.

I think the word has gotten out not to use the fuse "piggyback’ type connector. I do not condone piercing the insulation in all but the most "no other way’ type situations, at times backprobing can get so problematic that you actualy damage the connector. Gotta look these cases over good, one hole in insulation or a connector that has lost tension, no good choice here.