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How to find a leak current in the power-supply?

The leakage current in the car — is a common fault with MDM, sooner or later, faced by all drivers. This can happen even with new cars. If this happens, it is important to quickly identify and eliminate the current will flow. In this article you will find out the reasons that may lead to leakage, as well as how to solve this problem.

How to find the leak current in the power-supply?

What could be the reasons for electricity leakage?

Cerda equipment used in the car, be the loss of current source can:


The security system should continue active work, when all the other devices in the car a rest. It is very often the cause of power loss as it is one of the most important customers.

In many modern alarms have a transceiver that periodically communicates with the control key ring, in addition, they are equipped with GPS systems, GSM and other useful options. Many manufacturers of car alarms tend to minimize the level of electricity consumption when the system is armed  .


It is a device often causes a loss of power on the network. Most of the models to maintain the volatile part of the memory (saving user settings, timing, etc.) are constantly in need of the power supply. If you find that the device is defective, it will leak through the radio talk. But even serviceable radio may give a small leakagec urrent to about 10 mA.

How to find the leak current in the power-supply?

The engine control unit

This voltage is supplied portion   always, even if the unit is in good condition, the leak will still be the case, the truth is quite small — to a pair of units of milliamps. This is not a critical component.


In the voltage generator comes always with a positively charged terminal of the battery. If there are problems in his work, then discharge the battery generator is only half an hour. In good condition, he constantly consumes power, only a small amount, up to a few microamperes.


If the machine is plugged, the serviceable starter should not consume energy,   despite the fact that it constantly, even during parking, a voltage is applied. Consumption usually begins only at the time of starting the engine.


Often the surface of the terminals battery plaque formed — it is also electrolysis, which leads to discharge the starter battery. It's all in turn leads to energy leakage. But also do not forget about such a concept as an internal battery self-discharge, which is triggered by a violation of the integrity of the battery plates or low-quality electrolyte. For old batteries that have worked for more than a year, this figure could exceed the leakage current of the vehicle.

How to find the leak current in the power-supply?

The negative impact of the loss of current in the onboard network  

Because of the leaks can be a variety of troubles, including:

Run the battery down — this is one of the most common effects. In this case, it is quite harmless, and quickly eliminated. Calculate leakage is quite easy for the exponent of 0.5 A for 10 hours of parking machines   battery loses about 5 Ah its charge, and after 100 hours – 50 Ah. That is, the battery is fully drained in just four days parking. To avoid this, it is recommended to remove the battery cable to disconnect it from the network until the machine is standing motionless in the garage.

Failure individual blocks — this is a significant problem. At a current of 0.5 A dispersion index of force will be about 6 watts. If the energy is lost on any one element, such as a transistor or a chip portion of the control unit, it starts to become very hot, which would lead to its complete rejection.

Ignition wiring — the most dangerous and serious investigation. For example, the leak at 1 A, can lead to the fact that the power dissipation is 12 watts order. Such power itself can not cause a fire, but the seal under such conditions may start to melt. This triggers the closure of the wiring, then in the process will take a large current value, and they will be a source of ignition. All this leads to the so-called “spontaneous combustion” car.

How to find the leak current in the power-supply?

How to check if whether the vehicle electric leakage?

In fact, check if their on the net leakage electric cars can be quite easy with a special device — multimeter.

The sequence of actions in this case must be as follows:

  • 1. Beforehand get layout automotive fuses. As a rule, all specified by the manufacturer in the manual for the vehicle. Sometimes you can find a transcript of the location of the fuses on the unit's cover with fuses, but do not all manufacturers.
  • 2. Remove the positively charged terminal of the battery. It is important that   all installed in the car electricity consumers and the ignition was turned off before checking .
  • 3. Take a meter and activate the mode in which the constant current contact device is measured at the same time are connected to the terminals, it is best for them to put on a special attachment crocodiles, so it will be more convenient to work, because the contacts are securely fastened.
  • 4. When connecting strictly polarity: positive (red) is mounted on the contact “+” battery terminal and the negative – on the removal of the clamp, which goes to the car equipment. Please note that the connection must be carefully protected from possible contact with the body of the vehicle (it is enough to temporarily isolate this place a cloth). This is important to avoid short-circuits.
  • 5. The display meter will display information about the leakage current. If the value is less than 0.2 A, it means that everything is within normal limits, and additional control and inspection is not required. If the display device was highlighted value above 0.5 A, it is bad, because it is a critical component. In this case, you need to implement a special set of actions to find and eliminate leaks. When the instrument displays from 0.2 to 0.5 A, the car owner can independently take a decision to commit any further action.
  • 6. At this stage, the search for the exact cause of the leakage current and its source. Here you may need an assistant who will consistently remove the fuses and return them back to their seats. The second man at the same time should constantly monitor the dynamics of the meter readings.
How to find the leak current in the power-supply?

If after the fuse has been removed, the readings do not change, then the current is not flowing out through it. If, for example, when removing the fuse, which is responsible for the body control unit, leakage current sharply decreased, it is necessary to carefully check the other fuses from his chain, responsible for the windshield wipers, lights,   washer and other components of a body of equipment. Thus, it is necessary to go through each fuse, the only way it will be possible to assess how performance multimeter will vary on different parts of the circuit. This will help to find the exact cause of the power loss.

  • Advanced testing method, there is no longer need to attract mates. First battery terminal snapped back. Fuses also sequentially turned off. Wherein the multimeter probes are connected to the connectors short fuse, it allows controlling current within a particular circuit. The method, of course, is quite time-consuming, but it allows you to get more accurate data.
  • 8. Once decrypted, the location of all the fuses in all circuits where there is a leak, you can begin to search for a specific reason. There is not hinder the experience and knowledge of working with circuits in automotive electrical. The most common causes are usually:
  • circuit wiring;
  • breakdown of the individual electronic components;
  • sticky relay.

Once the cause is found, the leakage should be eliminated. Temporarily problem can be solved. To do this, simply do not return the fuse, which showed the presence of current losses in place. For example, if during the measurements, it became clear that leaks cause — malfunction of the car, then the corresponding fuse can be turned off at the time of parking   cars.

In addition, to reduce the leakage can be by treatment with contacts, connection terminals, conductors and connectors with special protective means. To do this, you can take a simple silicone grease or spray.

How to find the leak current in the power-supply?

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