You will need
- The tester, permitting resistance measurement in the range of 100-1000 ohms.
Prepare a diode bridge to check. Disconnect one of the connections of the diodes together. If the connections are made by soldering, desolder two diodes in place of their connection. It is necessary to exclude the influence of complex faults (breakdown of several diodes) on the test results. If the diode bridge is configured as an integrated Assembly, and preparation for verification is not required.
Prepare tester to work. Switch the mode to resistance measurement with a maximum value of 1000 ohms. Test the tester, the circuit closing contacts of the probes. The displayed resistance should be equal to zero.
Test the diodes. Measure the resistance of each diode separately in two directions. Connect the probe of the tester to the pins of the diode. Read the resistance value. Adjust the probes swapped. Again, remove the statement. A healthy diode should have a resistance of several hundred ohms in one direction (depends on the semiconductor material - silicon or germanium) and an infinite resistance in the other. If the diode has a low resistance when measured in both directions, then the diode is broken circuit. If in both directions the diode has infinite resistance, then the diode is broken open. Diode bridges in the form of assemblies are checked similarly. Verifiers from the breakdown of several diodes, able-bodied diode can be identified as faulty. But it doesn't change anything, since you have to replace the entire Assembly.
Avoid testing diodes with connection using these bulbs. The current going through the diode may exceed the maximum allowed value for the diodes in this series and he will be out of action.
You can do a quick check of the diode bridge for malfunction by measuring the resistance in two directions between its outputs. The bridge needs to pass a current in one direction and not to miss in the other. Not the fulfillment of this condition indicates a faulty diode bridge. Implementation, however, does not mean that the bridge is serviceable.
Advice 2: How to check the diode bridge generator
Semiconductor–diode used in those parts of the circuits which is necessary to pass current in one direction only, excluding the back passage. Therefore, a defective diode or do not pass current through itself, or passes him in both directions. That is absolutely unacceptable in the conditions of normal operation of the automobile generator, the construction of which is included a diode bridge.
You will need
- - ohmmeter,
- - indicator light
- - insulated wire – 1 m.
In cases of malfunctions related to the production of the generator the charging current, diagnostic checks, among other things, the operation of the diode bridge.
To perform this check, without removing the generator, enough to power off the on-Board network from the battery.
Diode test to determine their short-circuit begins with a voltage supply with pigtail attached at one end to the positive battery terminal and the other to the generator to terminal "30". The control light is switched between the generator housing to the negative terminal of the battery.
If the test light is on, it indicates a short circuit diode, therefore, the generator must be removed from the engine for execution of repair, which reduces to the replacement of the diodes separately, or the diode bridge as a whole.
For this there is a diode bridge, which is located at the rear of the generator. Diode - a device with two terminals that allows electrical flow to flow through it in one direction. The diode bridge usually has nine or eleven diodes (three additional).
In order to prevent bridging of the aluminum heat sink plate is covered fully or partially by a layer of insulating material. The terminals of the windings of the stator are welded/soldered or fixed screw connection to the mounting pads of the rectifier Assembly of the generator. How to check the diode bridge of the generator.
Advice 3: How to ring the diode bridge
Disappears when the battery on the car and does not help replace the brushes, so the problem is hidden in the generator. To start Troubleshooting you should check the diode bridge.
You will need
- - A set of keys;
- - screwdriver;
- - soldering iron 100W;
- - a multimeter or ohmmeter.
For Troubleshooting remove the generator from the machine. Depending on the brand of machine and model of the engine, its location can be different, in some cases greatly complicates the procedure of dismantling alternator. To remove the alternator, loosen the hinged bolts, then loosen the belt tension with a key, turning in the adjustment bolt tension the generator belt until when you will be able to remove the belt from pulleys. If you are not going to change the alternator belt, remove the belt just from the alternator pulley, if the other belts prevent to remove it from the pulley. After removing the belt, disconnect the connector with the control wires and remove the nut which dragged the power lead to the terminal of the diode bridge of the generator. Releasing the generator, remove the fully hinged bolt and remove the mounting bolt connecting the body of the generator breaker. After that, remove the alternator from the engine compartment.
Disassemble the generator. To do this, use socket wrench remove the bolts holding the front and rear of the alternator, then carefully disconnect housing. Try to keep when disassembling the housing, the stator remains on the front wall, since the stator winding is directly soldered to the diode bridge.
Remove the diode bridge from the front wall of the generator. Using a Phillips screwdriver, loosen the mounting bolts of the diode bridge, then use the Allen key Unscrew the retaining nut from the positive terminal on the alternator. Look closely, perhaps negative terminal of the bridge also is secured to the body by a separate nut. If so, loosen this nut. After you Unscrew all the mounting bolts, remove the front wall of the generator.
Desolder the diode bridge from the windings of the generator. Preheat a powerful soldering iron, solder its tip, after which you will be able to easily unsolder the leads of the windings of the stator from the bridge. Otpaivala the terminals of the windings, slowly, applying the heated soldering tip to the soldering spot and at the time of melting the solder, using a flat screwdriver, as capture the insights of the bridge from the terminals of the windings. Desolder all 4 points, then the diode bridge will be released and it will ring.
Using an ohmmeter, check each diode individually without dismantling the construction of the bridge, as the other diodes, if they are OK, do not affect the measuring result. The diodes should show conductivity only in one direction. If you have a DMM, pay attention to the readings. They should be close. This device shows not only the conductivity but also the voltage drop across switching diode. Normal voltage drop is 170-250 mV and depends on the specific brand of diodes. In the opposite direction, no conductivity should not be.