An initial quick check of the alternator can be performed directly on the vehicle.
Checking the alternator on vehicles with ZMZ-402 type engine
Vehicles with ZMZ-4025 and ZMZ-4026 engines are equipped with 16.3701 or 191.3701 alternators, which do not have a built-in voltage regulator.
These alternators operate with an external transistor voltage regulator type 13.3702-01 or 50.3702, which has electronic protection against short circuits in the alternator field winding circuit.
It is more convenient to perform the work with two people.
Start the engine, let it run for a few minutes, then, by pressing the accelerator pedal, bring the crankshaft speed to 3000 rpm–1.
Switch on the consumers: high beam headlights; heater fan; windscreen wiper; hazard warning lights.
In this mode, measure the voltage at the battery terminals, which should be above 12 V.
If not, the alternator windings are faulty (open or short circuit), the voltage regulator with brush assembly is faulty, the slip rings are oxidised or greasy, the brushes are worn or «sticking».
To confirm a voltage regulator fault – switch off all consumers except the side lights and measure the voltage at 1000-1200 rpm–1, which should be between 13.8 and 14.5 V.
To check the alternator field circuit, disconnect the connector from the regulator.
Connect a voltmeter or test lamp to the «Ш» terminal of the connector and the voltage regulator housing.
Switch on the ignition.
If there is no voltage (the lamp does not light) – one of the following faults is possible: poor contact of the field winding with the slip rings; open circuit of the field winding; brushes «sticking» in the brush holder channels; burning, oxidation and severe wear of the rotor slip rings.
Checking the alternator on vehicles with ZMZ-405, ZMZ-406 type engine
Engines of the ZMZ-406 and ZMZ-405 families are equipped with 9422.3701 or 5122.3771 alternators with built-in integrated voltage regulators.
Start the engine, let it run for a few minutes, then, by pressing the accelerator pedal, bring the crankshaft speed to 3000 rpm–1.
Switch on the consumers: high beam headlights; heater fan; windscreen wiper; hazard warning lights.
Measure the voltage at the battery terminals, which should be above 12 V.
If not, the alternator windings are faulty (open or short circuit), the voltage regulator with brush assembly is faulty, the field winding rings are oxidised or greasy, the brushes are worn or «sticking».
To confirm a voltage regulator fault – switch off all consumers except the side lights and measure the voltage at 1000-1200 rpm–1, which should be between 13.5 and 14.2 V.
The removed voltage regulator can be checked as follows.
Connect a lamp (21-35 W, 12 V) between the brushes.
Connect +12 V to terminal «D» and ground to the «ground» terminal.
The lamp should light up, and then go out when the source voltage increases within 13.5–14.2 V.
If the lamp lights in both cases, replace the regulator.
Checking the rectifier unit diodes and additional diodes is described in the article - "Alternator 9422.3701"
We recommend replacing the rectifier unit as an assembly if its elements fail.
Replacement of individual diodes is permitted, but will require re-pressing them into the holder – an operation that requires care and skill.
