Rectifier block valve test circuits
A - check at the same time «positive» and «negative» valves; B - check «negative» valves; B - check «positive» valves; 1 - generator; 2 - control lamp; 3 - battery
A good valve 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).
A short circuit in the rectifier unit valves can be checked without removing the generator from the vehicle, 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 checking the valves of the rectifier unit.
Attention! In order to simplify the fastening of parts of the rectifier, three valves are on the body «plus» rectified voltage. These are valves «positive» and they are pressed into one plate of the rectifier block. The other three gates are «negative», have on the body «minus» rectified voltage and pressed into another plate of the rectifier unit or into the generator cover.
First check if there is a short circuit at the same time in «positive» and «negative» valves. For this «plus» connect the batteries to the clamp «30» generator, and «minus» through the lamp to the generator housing (see fig. Diagrams for checking the rectifier unit valves, position A). If the lamp is on, then some of «negative» and «positive» valves have a short circuit.
Short circuit only «negative» valves can be checked by connecting «plus» batteries with stator winding center plug (12 in fig. (see fig. Generator G-221, this plug is unmarked), A «minus» through the lamp with the generator housing (see fig. Schemes for checking the rectifier unit valves, position B).
Burning lamp means a short circuit in one or more «negative» valves.
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 much less common than a short circuit of the valves.
To check for a short circuit only in «positive» valves, «plus» connect the batteries to the clamp «30» generator, and «minus» – through a lamp with a plug of the central output of the stator winding (see fig. Rectifier block valve test diagrams, position B). Burning lamp will indicate a short circuit of one or more «positive» valves.
An open in the valves without disassembling the generator can only be detected indirectly 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 generator windings are in good order, and there is no short circuit in the valves, then the reason for the decrease in the output current is an open in the valves.