In order to make sure that the voltage regulator is working, turn off all consumers, except for the high beam headlights, and measure the voltage again. It should be between 13.2-14.7 V for generator 9412.3701 and 13.6-14.6 V for generator 371.3701.
The removed generator voltage regulator 9412.3701 can be checked by connecting a lamp between the brushes (1-5W, 12V), and to the conclusions «D+» and «weight» - power supply (only direct current «minus» - To «mass»!), first with a voltage of 12 V, and then 15–16 V. In the first case, the lamp should be on, in the second it should not. If the lamp is on in both cases, there is a breakdown in the regulator; if it is not on, there is an open or broken contact between the brushes and the regulator terminals. In both cases, the regulator should be replaced. To test the generator regulator 371.3701, the current source should be connected to the terminals «B» and «IN» («plus») And «mass» («minus»).
To check the valves of the rectifier unit, disconnect the wires from the battery, generator and from the output (conclusions) voltage regulator. «Plus» batteries through the lamp (1-5W, 12V) connect to outlet «B+» generator 9412.3701 (to the conclusion «30» generator 371.3701), A «minus» - to his body. If the lamp is on, then in the block «positive», and in the block «negative» valves have a short circuit.
To check for a short in «positive» valves «plus» connect the batteries through the lamp to the terminal «B+» generator 9412.3701 (with conclusion «30» generator 371.3701), A «minus» - with the output of one of the phase windings of the stator. If the lamp is on, one or more positive valves are broken.
To check for a short in «negative» valves «plus» connect the batteries through the lamp to the output of one of the phase windings of the stator, and «minus» - with the generator housing. If the lamp is on, one or more negative valves are broken or the stator windings are shorted to the generator housing. To exclude the short circuit of the windings, the generator is removed from the car and, having disconnected the windings from the voltage regulator and the rectifier unit, check their short circuit to «mass» lamp or ohmmeter. Alternator valves can also be checked with an ohmmeter without connecting the battery and test lamp.
The closure of additional diodes can be checked by connecting «plus» batteries through the lamp to the output «D» generator 9412.3701 (to the conclusion «61» generator 371.3701), A «minus» - to the output of one of the phase windings of the stator (to one of the bolts securing the rectifier unit). If the lamp is on, one or more additional diodes are broken.
The breakage of the main valves is determined by a sharp decrease in the recoil current (voltage drop under load). However, it can also be caused by an open or short in the generator windings. An open in additional valves can be identified by low voltage on the plug «D» alternator 9412.3701 or plug «61» generator 371.3701 (below 14 V) at low and medium frequency of rotation of the generator rotor.
Determine the health of each diode (main or additional) It is possible only on the removed rectifier unit with an ohmmeter or test lamp. In the event of failure, the rectifier unit is recommended to be replaced as an assembly. It is possible to replace individual valves, however, for the main valves, they will need to be repressed in the holder - an operation that requires accuracy and skill. The stator and rotor windings are checked with a special flaw detector or an electronic oscilloscope - according to the shape of the voltage curves.