In what cars wiring can rot quickly, and why it happens

Rotting wiring is found in cars of different classes and countries of production, from cheap Chinese cars to premium German ones. But there are some cars that suffer from electrical rot the most.


BMW 5 and 6 series cars from 2003-2010 were recalled due to “decayed” wiring. There was an official recall campaign to which owners of these cars were invited. They have corrosion on the threaded connection of the plus wire to the battery due to the influence of road reagents. This causes electrical malfunctions, resulting in the inability to start the engine. Also the wiring often melts, which may provoke a fire.

Lifan X60

Chinese crossovers Lifan X60 2013-2018 years of production have problems not only with the electrics, but also with the body: the metal rots badly. But if this can be corrected by body work, then it is much more difficult to identify and fix faults in the wiring. This car has moisture accumulating under the floor upholstery, and after a few years of use, the wiring is severely damaged. Short circuits often occur, which can lead to a fire.

Nissan Pathfinder

There are thick braids of wires running along the frame of the third-generation Nissan Pathfinder SUV. They get water and dirt deposited on them during the car’s use. This leads to rotting of both the harness and the frame. Short circuits often occur in cars of this model. But, since it is quite difficult to detect the problem, the service will most likely offer you to replace the part, and this will cost serious financial expenses.


We are talking about the X-Class pickup truck, which is built on the basis of the Nissan NP300 Navara. In this vehicle, the wiring is located close to the wheel arches. If they are not protected, they get dirt from under the wheels. Once it settles, it causes the wiring to rot. This is fraught with optic failure and problems with engine starting.

Most often malfunctions with electrical wiring are encountered in old cars. But sometimes new ones are also guilty of this, especially if they are constructively illiterate, as the abovementioned models. If you buy a used car, you can’t be sure that it has not been in serious situations, or that the electrics haven’t been tampered with by masters. And meanwhile the work of professional electricians at service stations is not cheap.

The structure and functions of the wiring

The electric wiring is a system connecting various electronic assemblies and indicators of the car. It consists of hundreds of different joints: each indicator has four or five wires, which are connected in the central harness, interacting with the ECU, intermediate indicators and relays. The wiring harness supplies voltage to the fuel system. It is also responsible for keeping the engine running normally.

A short circuit in one segment can damage the entire wiring harness of a car. Fuses can partially help prevent the system from failing, but they are not always effective.

As mentioned above, there are specific causes of wiring defects in certain makes of cars. If after two or three visits to the service center you failed to identify the specific cause, read on internet forums of car enthusiasts and professionals what they write about your car. It will help to reveal the direction of the problem search.

What elements of electrical wiring are most often damaged

The following elements are most susceptible to ” rust”:

  • The power wiring harness – the element under the hood that connects the indicators that are responsible for the proper functioning of the engine.
  • Fuse box – connected to the engine wiring harness, includes a box with relays and fuses, located in the underhood space.
  • ECU harness – a braid of wires that connects parts of the under-hood wiring and control unit. Damage in this system blocks engine operation.
  • Wires of lighting devices, electrical elements of the instrument panel – are located under the front panel in the cabin, branching off to the front and rear lighting devices.
  • The braid going to the turbocharger in cars with a turbine – malfunctions in this node are fraught with serious consequences for the car.
  • Blocks of relays and fuses, located in different places in cars of different makes and models – you should find out their location and save the scheme.

Causes of wiring rot

Rotting leads to the fact that the electrics begin to work incorrectly: the headlights stop turning on, the car does not want to start at all. There are other signs, the cause of which is rotten wiring. But it is quite difficult to determine the malfunction even in the diagnostic centers.

So why can electrical wiring rot quickly? Experts name the following factors:

  • Moisture ingress, including under the floor upholstery – because of this, the elements of the wiring get wet;
  • oxidation – it occurs due to moisture: the contact weakens or disappears altogether;
  • Temperature changes – they cause condensation;
  • Constant vibrations while driving – they can lead to the rupture of thin wires.

In older cars, problems with wiring are more common. Over time, elements decay and need to be replaced.

The cause of rotting of the wiring can be an improper technical decision of the manufacturer. For example, in some SUVs and parkettes, the corrugations with wiring are attached directly to the frame. It makes the process cheaper, but moisture gets on the frame in rainy weather through the leaky corrugation, and in winter it is added with reagents. This leads to the destruction and shorting of the wiring.

Due to an engineering error in the design of some vehicles, the wires come close to the wheel arches. If the arches are not protected by plastic, dirt from under the car’s wheels inevitably gets on the wiring, causing it to rot. The result is electrical failure.

Another mistake made by the engineers is incorrect wiring under the hood. If moisture penetrates inside the harness, the engine won’t start.

Under the influence of temperature fluctuations, contacts oxidize, and then problems with the wiring are inevitable. The main thing is to detect them in time and take measures for their elimination: cleaning wires and their insulation.

In addition, improper use of the car, insufficient attention to its maintenance or home-made repairs can lead to problems with electrical wiring. It is necessary to solve problems as soon as the first signs of wiring “decay” are detected.

Craftsman wiring repair problems

But problems with damaged wiring can be greatly exacerbated by the intervention of homebrewers. They often use solders, twists and terminals, which are the enemies of normal car operation. The solders oxidize when water gets in, causing complex short circuits.

If the twist in the wiring harness is not tightened enough, it will cause the indicators to malfunction. For example, in the Chinese car Ravon, the “heir” of Daewoo, twists in the wiring harness going to the ECU, as well as in the engine wiring lead to problems after the third year of operation. And replacement of wiring harness eliminates difficulties only for a while, then they come back.

The owners of Ravon have to appeal to the workshops, where they solder the cords. But this is also only a temporary solution to the problem.

If you apply the terminals, only with quality terminals, which must be insulated to protect against the effects of moisture on the connections and contacts. Unfortunately, inexperienced craftsmen often do not adhere to this rule. And if you are planning to integrate new electrical appliances into the system, then you should definitely turn to professionals.

The problems of home-made repair will not reveal themselves at once. The car after that may still drive a certain kilometer, and then the difficulties will start. So always repair your “iron horse” by the professionals, in the qualification of which you have no doubts.

Before buying a car, especially if you are considering the above mentioned brands and models, make its thorough inspection for malfunctioning electrical systems. If there are suspicions that the wiring began to rot, it is better to refuse to buy and consider other options. This will allow avoiding problems with the further operation of the “iron horse”.

If a short circuit happened and the fuse burned out during the trip, you need to replace it and get to the nearest car service center. There you will be diagnosed to determine the cause of the short circuit. So always carry a few fuses with you that are suitable for different parts of the electrical system. Most of the time, electrical problems occur in cars over 10 years old. If you own such a car, you should always have electrical parts available.

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