A high-quality connection of wires in the electrical circuit of a car is the foundation for the safety and stable operation of all equipment. Many car enthusiasts neglect the use of tips, relying on twisting or soldering, but it is crimping provides the most durable and vibration-resistant contact. In conditions of constant shaking, temperature and humidity changes typical for machine operation, the mechanical connection must be performed flawlessly.
Using a specialized tool - crimper — allows you to deform the metal of the tip and the wire cores into a single monolithic structure. This eliminates oxidation of copper, heating at the point of contact and, as a result, the risk of fire in the wiring. In this article we will look at the nuances of choosing a tool, types of tips and a step-by-step algorithm of actions that will turn you from a beginner into a professional.
Incorrectly performed crimping often causes “floating” faults that are difficult to diagnose. When you know how to crimp wires correctly, you eliminate one of the main potential problems of electrical equipment at the installation stage. Let's take a look at what tools you'll need for this task and why all-purpose pliers aren't suitable.
Choosing a tool: why a crimper is better than pliers
The main mistake when installing wiring is trying to use ordinary pliers or side cutters to form a contact. These tools do not provide uniform pressure on all sides, which leads to deformation of the tip profile and a loose fit of the metal to the core. Crimper (or crimping pliers) is designed to compress the sleeve with a clearly defined force, forming the correct geometric profile.
There are several types of tools, each designed for different tasks. For automotive electricians, pliers with dies for NShVI (single) and NShVI2 (double) tips are most often used. More complex models may have adjustable stops or a ratcheting mechanism that will prevent the jaws from opening until the full crimping cycle has been completed.
⚠️ Attention: Never use a hammer to flatten tips. This “method” destroys the internal structure of the copper core, making it brittle, and does not guarantee electrical contact, which in a car with its vibrations will lead to rapid failure of the circuit.
When choosing a tool, pay attention to the material of the jaws. Hardened steel will withstand thousands of compression cycles without losing geometry, while cheap alloys will quickly “float” and the quality of crimping will become unpredictable. A good crimper should fit comfortably in your hand, as the process often requires considerable force, especially when working with thick wires.
Types of tips and their purpose in the car
Automotive wiring requires the use of specific types of limit switches, which differ from those used in a fixed home electrical network. The most common standard is ferrule lugs, known as NSHVI. They are a tinned copper tube with a plastic cuff that protects the wire from breaking and serves as an insulator.
To connect two wires to one terminal, for example, when distributing power from one fuse to two consumers, double lugs are used NSHVI2. Their plastic cuff has an elongated shape, allowing two stripped wires to be placed inside. This eliminates the need to make twists, which in a car are bad form and a source of problems.
- 🔌 NSHVI (single): designed for termination of one multi-core core, provides rigidity of the end of the wire for installation in the terminal block.
- 🔌 NSHVI2 (double): allows you to combine two wires without twisting, maintaining an aesthetic and reliable appearance of the connection.
- 🔌 Ring and fork: used for bolt connection (for example, to ground or battery terminal), they have a metal eye of different diameters.
- 🔌 Pin: used for connection to flat contacts of relays or fuses, often have an insulated or non-insulated heel.
It is important to select the tip strictly for the cross-section of the wire. If you use a terminal that is too large for a thin wire, the contact will be weak and the wire may jump out. A tip that is too small will require cutting off some of the strands, which will reduce current carrying capacity and cause heat. Proper selection of the ferrule size to the wire size is critical to preventing fires in the wiring.
Wire preparation: stripping and twisting
The quality of the future connection directly depends on how carefully you prepare the wire. The first step is to strip the insulation. The best way to do this is to use stripper or special pliers with adjustable knives that will not damage copper wires. Wires cut with a knife become a point of stress concentration and can break due to vibration.
The length of the stripped area must exactly match the length of the metal part of the tip. If you strip too little, the insulation will get inside the sleeve and there will be no contact. If there is too much, bare copper will remain outside, which can result in a short circuit or oxidation. Visually, the edge of the insulation should coincide with the edge of the plastic cuff after installation.
When stripping stranded wire, lightly twist the strands with your fingers before inserting them into the ferrule - this will help them fit smoothly into the sleeve and provide a tighter contact.
After stripping, many electricians recommend twisting the wires slightly to give them a cylindrical shape. However, if you are using a quality stripper and a properly sized tip, this may not be necessary. The main thing is to avoid fraying of the wires, when individual copper hairs stick out in different directions and may not get inside the sleeve.
Crimping technology: step-by-step instructions
The crimping process itself requires care and adherence to the sequence of actions. First, you need to insert the stripped end of the wire into the metal sleeve of the tip until it stops. Make sure that no veins are left outside or sticking out from under the cuff. The instrument is then grasped with a firm grip.
☑️ Checklist for ideal crimping
Place the tip in the appropriate socket of the crimper. For sleeve lugs, the socket cross-section is usually marked with numbers (for example, 1.5, 2.5, 4.0). Squeeze the tool handles smoothly but forcefully. If the crimper is equipped with a ratcheting mechanism, press it until you hear a characteristic click when the jaws come apart on their own.
After compression is completed, do not rush to remove the wire. Let the metal “rest” for a second to reduce internal stress. Then carefully remove the connection and check it. The tip should not rotate on the wire, and the wire should not be pulled out with a moderate tug. If you are using a double lug, make sure both wires are clamped evenly.
⚠️ Attention: If you are using a crimper without a position lock (ratchet), control the compression force visually and tactilely. An under-pressured tip is a time bomb that will begin to heat up under load, while a pinched tip can simply cut the wire strands.
For ring and pin terminals, the technology is slightly different: crimping is done in two places - first on the tube itself where the wire is inserted, then (if the design allows) on the shank. This ensures maximum secure fastening.
Comparison of characteristics of different compounds
To finally see the benefits of crimping, let's compare this method with other popular methods of connecting wires in a car. The table below shows the key differences in the most important reliability parameters.
| Parameter | Crimping (Crimper) | Soldering | Twist | Terminal blocks (Wago) |
|---|---|---|---|---|
| Vibration resistance | High (monolith) | Low (fragility) | Very low | Average |
| Installation speed | High | Low | High | High |
| Risk of oxidation | Minimum | Medium (fluxes) | High | Depends on type |
| Dimensions | Compact | Requires isolation | Requires isolation | Bulky |
As can be seen from the table, soldering, despite good contact, makes the wire at the junction hard and brittle. When the vehicle constantly vibrates, the solder joint will deteriorate over time. Twisting, even if done carefully, tends to weaken over time due to thermal expansion and contraction of copper.
Why is tinning before crimping prohibited?
Tinned wire (coated with solder) flows like plasticine under the pressure of a crimper. Over time, the solder “floats”, the contact weakens, sparking and heating begin. Only pure copper can be crimped!
Common mistakes and quality control
Even experienced craftsmen make mistakes if they treat the process carelessly. One of the most common problems is using the wrong ferrule for the wire type. An attempt to crimp a monocore (single-wire) wire with an NShVI ferrule is doomed to failure, since it is designed for multi-core cables.
A situation also often occurs when they try to stuff wires of different cross-sections or too many wires into one tip, cutting off the excess. This is a gross violation. Section - this is a characteristic that determines the current throughput, and its artificial reduction is unacceptable. Always select a tip with a margin or strictly in size.
- ❌ Insufficient insertion depth: the wire is not inserted all the way, some of the wires remain outside the cuff.
- ❌ Using pliers: leads to flattening of the sleeve into an oval, and not into the correct profile, contact is lost on the sides.
- ❌ Re-crimp: If you have already crimped the tip and realized that it sits crooked, you cannot crimp it again in another place - this will weaken the structure.
Quality control must be visual and mechanical. After crimping, lightly pull the wire and ferrule in different directions. They must move as one. If you hear a crunch or feel any play, the work needs to be redone. There is no place for “at random” connections in a car.
The main secret of reliability is not the compression force, but the exact correspondence of the cross-section of the tip to the cross-section of the wire and the use of a specialized tool with the correct jaw profile.
Can the tips be crimped with regular pliers?
Technically, you can insert the wire and squeeze it, but you won’t get good contact. Pliers flatten the sleeve, disrupting its geometry, and do not provide the necessary pressure for metal diffusion. This is a temporary solution that will quickly lead to oxidation and heat in a car.
Do I need to insulate the crimp area with heat shrink?
If you use NShVI lugs with a plastic cuff, additional insulation is usually not required, since the cuff already performs this function and goes inside the terminal block. Heat shrink is needed if you are using non-insulated ring or pin lugs in areas where contact with ground is possible.
Which tip is better: tinned or non-tinned?
For crimping, always choose tinned tips (they have a silver tint). Tinning protects copper from oxidation during storage and operation. Untinned (copper-colored) oxidizes faster, especially in high humidity conditions under the hood.