How to check the current leak in a car?

If your vehicle has a big exploitation term, the following problem may occur – the lossleakage of the current in the wire. Our conditions, both road and climatic ones, cause the deterioration, cracking and chaffing of the wire insulation layer and also the oxidation of connection sockets and terminal blocks contacts.

The oxidized contacts of the car wiring

Such leakages in the electric devices systems can cause the loss of engine grain, and in some cases – the short circuit and burning. In modern cars this risk is higher due to the variety of electric devices. This leakage usually happens in winter period, because during low temperature period the engine is not able to sustain its nominal volume for a long period. But more precise causes may include incorrectly installed devices (radio recorders, TVsets, amplifiers and alarm system), which are not in the basic car configuration. In case of daily car usage, the current leak is compensated with the charging of the engine via generator, but should the car be not used for a long time, the current leak may not allow the engine to get started. Many specialists recommend checking from time to time all the electric appliances in order to find possible current leak in the car. So, how can we check the possible current leak?

The checking and search for current leak do not require any special equipment, only multimeter and amperemeter which can measure direct current up to 10 A. It is essential before the checking to switch off all the electrical devices. Then put off one accumulator terminal from accumulator and moving the end between the terminal and the wire check the rate of current flow all along the chain.

The ideal measurements should be equal to zero, and the minimal and maximal ratings – 15 mA and 70 mA correspondingly. But in case your parameters are, e.g., 0,02-0,04, it is OK (the acceptable rate of leakage), because the ratings may vary according to the peculiarities of the electronic schemes of your car.

How to check the current leak

If you have found out that the measures are substantially higher than normal, then there’s a leakage in the car. Then it is necessary to find out the place of the leakage. Watching the values shown on amperemeter, put out all the fusible links from the fuse block one by one. When the ratings on the amperemeter decrease to the normal ones after taking out of one fusible link this is the evidence of your having found the current leak. In order to fix it, you should carefully check all parts of the chain: terminals, wires, sockets, consumers etc.

The algorithm of current leak checking

Should the current stay on the same level after taking out all the fuses, then check the rest of the wiring: the contacts, wires insulation, lanes in the fuses block. Check the generator, the starter and complementary equipment: the alarm system, radio recorder, because the devices are often the reasons of current leakage.

Even if you think that the current leakage is slightly higher than normal, and you shouldn’t pay much attention, the engine starts to lose the motor grain volume faster than gain in from the generator, and this will become observable during short rides in urban conditions. And in winter time such situation may become crucial for the engine battery.

If you are not able to do the procedure of current leakage checking yourself, then you’d better address the service station specialist.

Adam Henri 7 April 2022

Car mechanic with 10 years of experience in repairing and servicing cars of different brands. Main area: diagnostics and mechanics.