Checking the diode bridge with a multimeter, without removing the generator

Only a few drivers know how to test a diode bridge with a multimeter, and this knowledge can be very useful. This element plays an important role in the operation of the generator, and because of it the battery is charged correctly. Often, if there is any breakdown, drivers immediately drive their car to the service station. But often it's enough just to check the diode bridge with a multimeter, after which it will be possible to solve the problem yourself, leaving the money that would have to pay for the repair. Let's take a closer look at what kind of generator it is and why it is needed at all.

What is a diode bridge? Its principle of operation

This device in the charging element plays the role of a rectifier. To convert the current in the generator, 4 to 6 diodes are installed, and they are all combined into a single circuit, called a diode bridge. It is located directly in the generator itself.

The principle of operation of this element is simple: it passes the current generated by the generator to the battery and does not pass it in the opposite direction - from the battery to the generator. In this case in one direction a resistance of a certain value is created, and in the opposite direction resistance tends to infinity. If there is any malfunction with the bridge, the car electronics will fail. Rather, the battery will fail, and without it the car will not be corny, since the starter itself is powered by a battery.

Why does the diode bridge burn out?

Checking the diode bridge of the generator with a multimeter involves, among other things, finding out the reasons why the diode bridge breaks down. The most common reason is the accumulation of water inside. Often, after washing the car or driving through puddles, the bridge may burn out.

The second reason is reverse polarity at the battery terminals. This happens when the inauthority is lit or when the charger is connected to the battery. Of course, there may be more complicated reasons for bridge burn-out, but more often than not it happens for one of these two reasons. Therefore, try to avoid driving in deep puddles and charge the battery correctly.

How does the burned diode bridge affect?

If there are any problems with the battery, then first of all it is necessary to check the diode bridge with a multimeter. The battery is directly connected to this bridge. With its failure, two options are possible: the current does not go to the battery at all or goes very high. This can lead to an effervescence of the electrolyte.

Therefore, if you have a problem with the bridge, you need to solve it very quickly. Otherwise, you have to buy a new battery, but it's not cheap. Therefore it is better to have an idea of how the diode bridge is tested with a multimeter on 2110 and other models of the VAZ brand. At least there are 2 ways to check: using a multimeter or a regular light bulb. Let's consider both ways.

Checking the light bulb

The first is to remove the diode bridge from the generator. However, in the case of a light bulb without this you can do without. We take the bridge in assembled form and touch it to the battery terminal. Be sure to keep the contact constant and strong. Now take the light bulb and its contact (plus) touch the plus of the battery.

Now we alternately touch the other contact of the lamp to the contacts of the diodes, then to the contacts of the winding connection of the starter. If the bulb burns, it means that the bridge is "punched" and, therefore, it is non-working. Now, if the stages connect the circuit through one diode, you can identify the faulty element and replace it with a new one.

If there is a need to test the bridge to break the chain, then minus the bridge "throw" on the plus battery. Then we connect the lamp plus to the plus of the battery. Now we connect the free contact of the lamp to the elements, as described above. In this case, the lamp should be lit. If it does not burn at all or burns with a dim light, then a break in the diode circuit takes place.

Checking the diode bridge with a multimeter

As in the previous verification method with a light bulb, in this case it is also necessary to remove the bridge from the generator. When checking the diode bridge with a multimeter, each diode is checked separately. First, you need to turn the multimeter on in the "Wake Up" mode, but if there is no such mode, simply set the resistance to 1 kΩ. In this mode, when two contacts are closed, it will ring.

The bridge is divided into two parts: auxiliary and power diodes. Checking the diode bridge with a multimeter VAZ-2114 and other brands is the same for both parts. The principle is the following: a working diode in the direction of the battery will show a resistance equal to several hundred Ohms, in the opposite direction, the resistance will tend to infinity.

We connect the test leads of the multimeter to each contact of the diodes. And if the device displays a value that is different from the value after changing the probes in places, then this indicates that the diode has burnt out. This operation must be carried out for each diode.

If the resistance is very low

The second option when testing multimeter diode bridge generator VAZ-2109 and other models involves the display of zero values. This suggests that there is a cliff in the chain. If the readings are close to zero values (very low resistance), then it means that the diode is broken. The multimeter as a test device allows you to specify exactly which diode failed and determine the nature of the failure. When using a light bulb, everything is approximately the same, but with a weak charging current, it's more difficult to catch the correct operation. Therefore, the use of a multimeter is recommended, but if it is not, you can try to find a malfunction using a conventional light bulb.

However, the only plus of checking a light bulb is the fact that it is not necessary to remove the diode bridge from the generator. But without removing the generator it is impossible to check the diode bridge with a multimeter. Without removing the generator, you can not do this. There it is necessary to work with separate parts, but this gives a more accurate result.

When a non-operating diode is detected, it is replaced with a new one. Make it easy with a soldering iron. The diode itself costs a penny and is sold in any auto parts store. Its replacement also does not represent anything complicated, and it can be produced independently.

Conclusion

There is nothing complicated in this procedure. If you are more or less familiar with electronics and know how to use a multimeter, then you can check and replace faulty diodes yourself. For this, you do not need to contact the service station, where they will require money for verification and even more so for repairs.

All the elements that are necessary for repairing the diode bridge are available on sale. Yes, and the diode bridge itself is generally inexpensive, but there can only be problems with finding a bridge for a certain rare generator model.

Finally: if something is wrong with the battery, then you will be very lucky if the cause is just in the diode bridge. This, you can say, the consumable, which has to be changed from time to time. But the main thing here is to find out the fault in time, until the battery itself suffers.