Circuits for testing rectifier diodes
a - check at the same time "positive" And "negative" diodes; b - check "negative" diodes; c - check "positive" diodes; 1 - rechargeable battery; 2 - control lamp; 3 - generator; 4 - output "B" voltage regulator; 5 - wire of the common output of additional diodes
A good diode only allows current to flow in one direction. Faulty - may or may not pass current at all (open circuit), or pass current in both directions (short circuit).
If one of the diodes of the rectifier unit is damaged, the entire rectifier unit must be replaced.
A short circuit of the diodes of the rectifier unit can be checked without removing the generator from the car, after disconnecting the wires from the battery and the generator. You can check with an ohmmeter or with a lamp (1-5W, 12V) and battery as shown in Fig. Schemes for testing the diodes of the rectifier unit.
A break in the diodes without disassembling the generator can be detected either with an oscilloscope, or when checking the generator on the stand for a significant reduction (by 20–30%) the magnitude of the output current compared to the nominal. If the windings, additional diodes and the generator voltage regulator are in good order, and there is no short circuit in the diodes, then the reason for the decrease in the output current is an open in the diodes of the rectifier unit.
1. At the generator 37.3701, before checking, it is necessary to disconnect the output "B" (4 in fig. Circuits for testing rectifier diodes) voltage regulator from terminal "30" generator and wire from the output "IN" voltage regulator. Generators with new voltage regulator (see fig.Generator 37.3701, view "A") conclusion "B" missing and it is necessary to disconnect only the output wire "IN".
2. First check if there is a short circuit at the same time in "positive" And "negative" diodes. For this "plus" connect the batteries through the lamp to the clamp "30" generator, and "minus" to the generator housing (see fig. Schemes for testing rectifier unit diodes, and). If the lamp is on, then "negative" And "positive" diodes are short circuited.
3. Short circuit only "negative" diodes can be tested by connecting "plus" batteries through a lamp with one of the rectifier unit mounting bolts, and "minus" with generator housing (see fig. Schemes for testing the diodes of the rectifier unit, b).
4. Burning lamp means a short circuit in one or more "negative" diodes. It should be remembered that in this case, the burning of the lamp may also be the result of a short circuit of the turns of the stator winding on the generator housing. However, such a malfunction is less common than a short circuit of the diodes.
5. To check for a short circuit only in "positive" diodes "plus" connect the batteries through the lamp to the clamp "30" generator, and "minus" – with one of the rectifier block fixing bolts (see fig. Schemes for testing the diodes of the rectifier unit, in). Burning lamp will indicate a short circuit of one or more "positive" diodes.
Attention! In order to simplify the fastening of parts of the rectifier, three diodes are on the case " " rectified voltage. These diodes "positive" and they are pressed into one plate of the rectifier block. The other three diodes are "negative" - have on the body "minus" rectified voltage and pressed into another plate of the rectifier unit.