Automotive wiring is the nervous system of the car, on which the operation of all electrical equipment depends: from headlights and radio to engine sensors and ignition system. Poor quality wires or errors in their installation can lead to short circuits, overheating, and in the worst case, a fire. In this article we will look at how to choose wires for car wiring, what to pay attention to when purchasing and how to arrange them correctly to avoid problems in the future.
Many car owners are faced with the need to replace or modify wiring - be it installing additional equipment (cameras, amplifiers, alarms) or repairing standard electrical equipment after damage. However, not everyone knows that car wires differ from household ones not only in cross-section, but also in insulation material, flexibility and resistance to aggressive environments. For example, an ordinary PVA wire from a hardware store will last in a car for several months at most - its insulation will crack from temperature changes, and the copper conductors will oxidize from moisture.
We analyzed offers from leading manufacturers (such as Kettenbach, Hella, Molex), studied the reviews of auto electricians and compiled a checklist of criteria that will help you choose reliable wires for any task - from replacing a burnt-out section to a complete overhaul of the electrical system. We'll also tell you why wires with silicone insulation can withstand up to +200Β°C, while standard PVC begins to melt already at +80Β°C β this is critical for the engine compartment.
1. Types of car wires: how they differ
There are three main types of wires used in a car, each of which is designed for its own operating conditions. They cannot be replaced with each other - this will lead to premature wear or emergency situations.
- π₯ High voltage wires β for ignition systems (spark plugs, coils). They have reinforced insulation and metal tips. Example: Tesla GT-40 or NGK Resistor.
- β‘ Low voltage power cables β for powering consumers (headlights, starter, audio system). Usually multi-core, color-coded. Popular brands: Hella FLRY, Kettenbach KFZ.
- π‘ Signal wires β for data transmission (CAN bus, sensors). Thin, often shielded. Example: Molex STP.
It is worth highlighting battery cables - they must withstand starting currents of up to 500β1000 A. The cross-section (at least 16β25 mmΒ² for passenger cars) and materials are important here: the best options are copper in silicone insulation (for example, Kettenbach AKKU) or aluminum-copper alloys (cheaper, but less reliable).
β οΈ Attention: Never use wires with aluminum conductors for battery terminals - they oxidize and lose conductivity. This is one of the main reasons for βfailuresβ when starting the engine in winter.
2. Wire cross-section: how to calculate and not make mistakes
An insufficient cross-section leads to a voltage drop and overheating, and an excessive cross-section leads to unnecessary costs and difficulties during installation. For automotive wiring, the cross-section is selected according to maximum current, which will pass through the wire, and length of the section.
The calculation formula is simple:
S = (I Γ L Γ 0.0175) / ΞUWhere:
Sβ cross-section in mmΒ²,I- current in amperes,L- wire length in meters,ΞUβ permissible voltage drop (usually 0.5β1 V).
| Consumer | Current (A) | Recommended cross-section (mmΒ²) |
|---|---|---|
| Headlights (halogen) | 5β10 | 0.75β1.5 |
| Starter | 100β200 | 16β25 |
| Audio system (amplifier) | 20β50 | 4β10 |
| Radiator fan | 15β30 | 2.5β6 |
To simplify, you can use ready-made tables from manufacturers (for example, Hella or Bosch), but remember: they often indicate minimum values. If the wire will pass near heating elements (exhaust pipe, engine), take a cross-section with a margin of 20β30%.
3. Core material: copper vs aluminum vs alloys
In 90% of cases, they are used for automotive wiring copper wires - they have better conductivity and corrosion resistance. However, there are nuances:
- πΉ Pure Copper (CU) - the best option for power lines. Marking: H05V-K (flexible) or H07V-U (single-core).
- πΈ Tinned copper (CU+Sn) - coated with a layer of tin to protect against oxidation. Ideal for the engine compartment. Example: Kettenbach Litzen.
- πΆ Copper Aluminum (CCA) - a cheap alternative, but fragile and prone to oxidation. Suitable for temporary connections only.
Aluminum wires are practically not used in cars - they break when bent and require special terminals (with anti-oxidation paste). The exception is some budget models VAZ or UAZ, where aluminum is used in standard wiring to reduce cost.
β οΈ Attention: If you find aluminum wires in your car (for example, in harnesses GAZelle or old Volg), under no circumstances connect them directly to copper strands - this will lead to electrochemical corrosion. Use terminal blocks with paste or crimp sleeves.
To check the material of the cores, pry the insulation with a knife: copper has a reddish tint, aluminum is silver, and aluminum-copper is yellowish (due to the steel core).
4. Insulation: that withstands heat, oil and vibration
The insulation of automotive wires must withstand:
- π‘οΈ Temperatures from β40Β°C to +120Β°C (for under-hood wires - up to +200Β°C).
- π§ Moisture and oils - especially relevant for wiring in the engine compartment.
- π Vibrations β the insulation should not crack due to constant micro-movements.
The most common materials:
| Material | Benefits | Disadvantages | Application |
|---|---|---|---|
| PVC | Cheap, flexible | Melts at +80Β°C, resistant to oils | Salon, doors |
| Polyethylene (PE) | Moisture resistant, UV resistant | Hard, cracks in the cold | External harnesses |
| Silicone (Si) | Heat-resistant (up to +200Β°C), elastic | Expensive and difficult to install | Engine compartment |
| Thermoplastic elastomer (TPE) | Oil resistant, flexible | More expensive than PVC | Fuel pumps, sensors |
For critical areas (such as oxygen sensor wires or injectors), use double insulated wires - for example, Hella FLRY-B (outer layer made of polyamide, inner layer made of modified PVC). This will protect against breakdown to ground due to friction against metal parts.
How to check insulation for cracks?
Inspect the wire under bright light, bending it at a 90Β° angle. Microcracks will be visible as white stripes. You can also use a magnifying glass or a tester: attach one probe to the core, and run the other one along the insulation - if the resistance is not infinite, the insulation is broken.
5. Color coding: standard vs chaos
In automotive wiring, the colors of the cores are not random - they follow to DIN 72551 standard (for European cars) or GM Standard (for American). However, some manufacturers (especially Chinese) ignore these rules, which complicates repairs.
Primary colors according to DIN:
- π΄ Red β plus from the battery (constant +12V).
- π΅ Blue β plus after the ignition switch (ignited +12V).
- β« Black β mass (minus).
- π’ Green β signal wires (CAN, sensors).
- π‘ Yellow β lighting (headlights, dimensions).
In Japanese cars (for example, Toyota or Mitsubishi) are often used striped markings:
- π΄Red with black stripe β +12V from the battery.
- π΅Blue with white stripe β tachometer signal.
β οΈ Attention: Before replacing wires, always check with wiring diagram of a specific model! For example, in BMW E39 the yellow wire may mean positive from the generator, and in VW Passat B5 - ABS signal. An error will result in a short circuit.
πΉ Make sure the colors match your car's scheme
πΉ Check the flexibility - the wire should not break when bent
πΉ Inspect the insulation for cracks or thickening
πΉ Measure the cross-section with a caliper (often underestimated!)
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6. Wiring installation: mistakes that kill electricians
Even the best quality wires will fail if they are not installed correctly. Here 5 most common mistakes and how to avoid them:
- Gasket without corrugation. The wires rub against the metal of the body, the insulation wears off β short circuit. Always use corrugated tubes (for example, Hella Conduit) or textile braid.
- Twisting instead of crimping. Twisted wires oxidize, heat up and burn off. Use terminal blocks (for example, Wago 221) or crimp sleeves with heat shrink.
- Constriction with clamps. Compressed wires lose their cross-section and overheat. Tighten the clamps until the wire can be moved by hand.
- Ignoring fuses. Each new consumer (for example, additional light) must be protected separate fuse, designed for 120β150% of the maximum current.
- Soldering without insulation. Solder oxidizes over time. After soldering, always apply hot melt adhesive or electrical tape 3M Super 33+.
Pay special attention passing through partitions (for example, from the passenger compartment to the engine compartment). Use rubber bushings or sealed connectors (for example, Deutsch DT) to prevent chafing and moisture ingress.
The most common cause of fire in a car is not a short circuit, but bad contact at joints. It leads to local overheating up to 300Β°C and ignition of the insulation.
7. How to choose wires for specific tasks
Let's sort it out top 5 scenariosproblems faced by car owners, and suitable wires for each:
- Replacement of standard wiring.
Use stranded copper wires with insulation TPE or polyethylene (for example, Hella FLRY-A). The cross-section is the same as the original, the color is according to the diagram.
- Installing an amplifier or subwoofer.
Needed oxygen free copper wires (OFC) with a cross section of 4β10 mmΒ² (for example, Kettenbach KFZ 6mmΒ²). Be sure to use fuse next to the battery (60β100A).
- Wiring for the winch.
Cross-section not less than 25 mmΒ², insulation - silicone or heat resistant PVC. Example: Molex Mega-Fit. Connect only via solenoid!
- Repair of high-voltage wires.
Only carbon core silicone wires (for example, NGK Blue or Tesla GT-40). Resistance - 5β10 kOhm per meter.
- Connecting LED strips.
Enough flexible wires 0.5β0.75 mmΒ² (for example, Hella FLRY 0.75). Be sure to use voltage stabilizer (12V β 5V/12V).
For temporary connections (for example, during diagnostics), you can use wires with crocodiles (for example, Kettenbach Krokodil), but don't leave them for too long - they're not designed to withstand vibration.
FAQ: Answers to frequently asked questions
Is it possible to use household wires (PVS, SHVVP) in a car?
No. Their insulation does not withstand temperature changes, oils and vibrations. The maximum is a temporary connection in the cabin (for example, to charge a phone), but not longer than a few days.
Which wire is better: single-core or stranded?
For car stranded only! Single-core wires break due to vibrations. The exception is short sections in fixed harnesses (for example, in a fuse box).
What is the difference between the wires for injection and carburetor cars?
In injection machines, the requirements for noise immunity (due to the ECU and sensors). Use shielded wires for signal lines (for example, Molex STP). In carburetor engines you can get by with standard ones. Hella FLRY.
How to protect wires from rodents?
Rodents do not like:
- π§ The smell of onions or garlic (wipe the wires with juice).
- πΆοΈ Hot seasoning (place pepper bags in the engine compartment).
- πΆ Special repellents (for example, Liqui Moly Marder-Schutz).
Also helps metal braid (for example, Techflex F6).
What wires are needed to connect the rear view camera?
Enough coaxial cable RG-59 (for video) and two-core wire 0.5 mmΒ² (for food). The main thing is to shield the video line to avoid interference from other devices.