How to find the leakage current in the car with a multimeter

Long-term parking of the car without movement and periodic warming up of the motor can sometimes adversely affect the ability to start it. In response to the key scrolling, clicks from the relay circuit will be heard in the lock, but the engine scrolling will not occur.

This situation suggests that there was a complete or partial (to a large extent) discharge of the power source in the vehicle. It is impossible to call this a self-discharge if the battery was fully operational and the parking period was not calculated in several months. The reason may be in an undesirable leakage process. How to check the leakage of current on a car with a multimeter, it is worth knowing the owners of the vehicle.


  • 1 The most common cases
  • 2 Electrical Accessories
  • 3 Permissible current leakage in the car
  • 4 Independent searches
  • 5 We identify problems

Most common cases

In order to prevent such a situation, it is important to take care of your car in a timely and efficient manner. The special attention is demanded by the batteries possessing a considerable operational experience. Checking the leakage current in a car with a multimeter should be carried out more often for electrical systems in which an old battery is installed. Poor condition of the terminals (scale or the presence of salts), wiring is in an unusable condition.

how to find leakage current in a car with a multimeter

The most popular reasons for which the charge goes to zero include:

  • working for a long time in the garage or in the parking lot not turned off head optics;
  • left foglights turned on;
  • working at a minimum volume of a radio or radio, especially if there is a subwoofer.

If all systems are turned off in time, it remains to use the measuring electrical equipment, but it is worthwhile to know in advance what kind of leakage should be in the car. It is important to get rid of such a factor, as it can lead not only to damage to the wiring, but also to the fire of the car as a whole. Among avtvolyubiteley there are several ways to implement monitoring.

Electrical Accessories

Exceeding the current leakage rate of the car battery can help all kinds of freelance equipment, which the owner of the car connected independently or with the help of third-party car services (non-branded). Annually such devices become more and more in the domestic market. However, it is worth paying attention to their quality.

When trying to identify a problem, it is recommended to pay attention first of all to such devices. These may include:

  • portable TV sets;
  • non-proprietary alarm;
  • powerful foreign amplifiers for audio systems;
  • additional lighting in the cabin;
  • set of abnormal speakers;
  • navigator.
See also: How to pick up the battery by brand of car

The manufacturer reliably protects the “native” automobile cables, therefore short circuits with them are possible only as a result of substantial damage to the insulation or their integrity. An example is the accident with the deformation of the car body.

how to check leakage current on a car with a multimeter

Unfortunately, stacked wiring from third-party electrical appliances is not always assembled in good faith and without complying with safety standards. It is necessary to take into account (to avoid) all operational capabilities that can make it unusable. Such cables lead to short circuits and due to inconsistencies in throughput loads, as they can save on inexpensive devices by equipping them with wires with insufficient cross-section.

Measure the leakage current in a car with a multimeter is necessary first of all on such equipment. The wiring may be laid too close to elements that heat up during operation, which can damage the insulation and create a short circuit.

Permissible current leakage in the car

It is important to consider that any vehicle contains in the design of permanent electrical consumers. They remain in the chain with the battery even after the other sources are completely disconnected. These elements include:

  • clock on the dashboard;
  • connected alarm;
  • electronic control unit, etc.

Such exploitation is related to the peculiarity of their work. If you disconnect them from the battery, it is necessary to reconfigure the equipment again each time. In this case, you need to know that there is a certain allowed rate of leakage current in the car, gradually discharging the battery.

However, this value is small, it can be determined by each user independently, by summing up the current of consumers. Usually, an alarm requires about 20 mA in the on mode, the clock “eats” no more than 1-2 mA. More accurate values ​​can be found in the instructions for use.

what is the rate of leakage current in the car

You need to know that a working car with high-quality batteries consumes no more than 40-80 mA.

Such readings are quite acceptable, because even one modern headlamp is able to take about 500 mA. With the allowable value “go to zero” even in the most frosty winter, it is rather difficult if the readings are observed.

Independent searches

Experienced motorists know the two most popular reasons:

  • network closure;
  • poor third-party device.

Due to the availability of modern low-cost diagnostic equipment, you can independently identify the problem. We will figure out how to find the leakage current in the car with a multimeter. At first we switch the device to the ammeter mode. It is important to remember that the current will detect a constant (not alternating!). Sufficient maximum will be 10 A, so pereschelivaem handle to the desired position.

See also: How much is the car battery

All measurements are carried out with the engine off. Existing consumers are disabled whenever possible. The device sometimes has to be connected to the open circuit To do this, we throw away the negative (negative) terminal and close the gap with a multimeter into this gap (one contact to the opened wire, and the second to the free contact of the battery).

You do not need to close the meter on the battery contacts, as this will lead to a short circuit and a fuse will burn in it. If the user did everything correctly, then an image with a number will appear on the monochrome display. This will be the current leakage current.

Determine whether the value falls into the required interval (up to 80 mA). When the device will show more, it is worth continuing the search for the consumer.

We detect problems

At the initial stage of monitoring, we conduct a visual inspection of the integrity of the wires. If there are abnormal situations, then we examine them more carefully for the detection of breakdowns. We test all limit switches.

When the inspection gave a positive result for the detection of corrosion or flashing, we proceed to the next stage. To do this, we translate the multimeter into ohmmeter mode (resistance monitoring). Check the selected cable section for crossing wires in the car.

Taking out alternately fuses must be traced to the presence of a spark in the contacts. If it is present, then it indicates the passage of current. We check the device depending on it.

The cause of the problem may be a generator. He can not only not charge the battery, but also discharge the battery in the engine off position. It is worth testing it. To do this, connect the red wire with a plus, and black - with a minus on the generator. Pre-translate the tester in the voltmeter mode.

When the battery is turned off, the readings should be 12.6-12.9 V. We start the engine, turn on the light, the radio and the stove. The maximum should be no more than 14.3 V, and the norm should be 12.8-13.4 V. Low values ​​are evidence of the problem.

Such simple tests can be carried out independently. This will help monitor the status of your battery.