Pic. 7.19. Generator components: 1 - pulley; 2 - sealing ring; 3 – rotor assembly; 4 - rear bearing; 5 - bearing holder; 6 - front bracket of the generator; 7 - front cover; 8 - stator; 9 - bar; 10 - voltage regulator and brush holder; 11 - brush; 12 - brush spring; 13 - dustproof ring; 14 - rectifier block; 15 - generator rear bracket
Disassembly (75 A model)
Loosen the three pinch bolts.
Pic. 7.20. Removing the generator front bracket
Insert a flathead screwdriver between the alternator front bracket and the stator and use the screwdriver as a lever to pry the (down) alternator front bracket (pic. 7.20).
Attention! Do not insert the screwdriver too far to avoid damaging the stator winding.
Pic. 7.21. Heating the bearing assembly with a soldering iron
It may be difficult to remove the alternator rear bracket because the circlip used to secure the rear bearing is in the way. To facilitate rear bracket removal, heat the bearing assembly with a 200W soldering iron (pic. 7.21).
Do not use a heat gun for heating, as this may damage the rectifier diodes.
Secure the rotor in a vise with the pulley side up.
Attention! Make sure the vise jaws do not damage the rotor.
Loosen the pulley nut, remove the spring washer, then remove the pulley and spacer.
Remove the alternator front bracket and two o-rings.
Remove the rotor from the vise.
Pic. 7.22. Disconnecting the outlet nut «IN» generator
Loosen the screws securing the brush holder and rectifier unit. Then unscrew the output nut «IN» generator (pic. 7.22).
Remove the stator assembly from the rear bracket.
Remove the dust ring from the brush holder.
Before removing the stator, unsolder the three wires of the stator winding from the main diodes of the rectifier unit.
Attention! When soldering/desoldering contacts, be careful that the heat from the soldering iron affects the diodes as little as possible. Perform these operations as quickly as possible.
Attention! Be careful not to apply excessive force to the diode pins.
Pic. 7.23. Places for soldering brush holder contacts
Before disconnecting the rectifier unit from the brush holder, unsolder the two pins soldered to the rectifier unit (pic. 7.23).
Rotor check
Pic. 7.24. Checking for a closed circuit between slip rings
Check for an open in the rotor winding. Check for continuity between slip rings (pic. 7.24).
If there is too little resistance (tends to 0), which indicates a short circuit. In the event of an open circuit in the rotor winding or a short circuit, replace the rotor assembly.
Resistance: Approximately 3.1 ohms.
Pic. 7.25. Checking the absence of a short circuit in the rotor winding «mass»
Check that the rotor winding is not shorted to «mass» (pic. 7.25).
Check for continuity between slip ring and core. If there is a closed circuit (short circuit «mass») replace the rotor assembly.
Stator check
Check for an open in the stator winding.
Pic. 7.26. Checking for a closed circuit between the stator winding terminals
Check for continuity between the stator winding terminals. If the winding circuit is open (resistance tends to infinity), replace the stator assembly (pic. 7.26).
Pic. 7.27. Checking the absence of a short circuit in the winding «mass»
Check the absence of a short circuit in the stator winding for «mass» (there is no closed circuit between the stator winding and the core) (pic. 7.27).
If the circuit is closed (resistance tends to zero), replace the stator.
Checking the positive output of the rectifier unit
Pic. 7.28. Checking the closed circuit between the output «positive» diodes of the rectifier unit and the output of the stator winding
Using an ohmmeter, check that the circuit between the terminal «positive» diodes of the rectifier unit and the output of the stator winding is closed (little resistance). Reverse the polarity of the ohmmeter probes and measure the resistance (if the resistance is small, i.e. the circuit is closed in both directions, so the diode is broken) (pic. 7.28).
Replace the rectifier assembly.
Checking the negative terminal of the rectifier unit
Pic. 7.29. Checking the closed circuit between the output «negative» diodes of the rectifier unit and the output of the stator winding
Using an ohmmeter, check that the circuit between the terminal «negative» diodes of the rectifier unit and the output of the stator winding is closed (little resistance). Reverse the polarity of the ohmmeter probes and measure the resistance (if the resistance is small, i.e. the circuit is closed in both directions, so the diode is broken) (pic. 7.29).
Replace the rectifier assembly.
Checking the three diodes of the rectifier unit
Pic. 7.30. Testing stator diodes
Test three diodes by connecting an ohmmeter to both terminals of each diode. For each diode, the circuit must be closed in only one direction (pic. 7.30).
With no closed circuit in both directions (or if there is a closed circuit in both directions) the diode is faulty and the rectifier unit (heat dissipating block) to be replaced.
Brush replacement
Pic. 7.31. Brush wear limit line
Replace the brushes if they are worn to the limit line (pic. 7.31).
Pic. 7.32. Places for soldering wires
Unsolder the brush wire and remove the alternator brush with spring (pic. 7.32).
Install the spring and new brush into the brush holder.
Pic. 7.33. Brush installation diagram
Insert the brush so that there is a distance of 2–3 mm between the edge of the brush holder and the boundary line on the brush (pic. 7.33).
Solder the brush wire to the brush holder
Disassembly (90 A model)
Loosen the outlet nut «IN» alternator and remove the rear cover.
Pic. 7.34. Places for soldering wires of the stator winding
Before removing the stator, unsolder the four wires of the stator winding from the main diodes of the rectifier unit (pic. 7.34).
Attention! When soldering / desoldering contacts, be careful that the heat from the soldering iron affects the diodes as little as possible. Perform these operations as quickly as possible.
Attention! Be careful not to apply excessive force to the diode pins.
Remove the stator assembly from the alternator rear bracket.
Remove the brush holder and rectifier unit.
Loosen the four pinch bolts.
Pic. 7.35. Removing the generator front bracket
Insert a flathead screwdriver between the alternator front bracket and the stator and use the screwdriver as a lever to pry the (down) alternator front bracket (pic. 7.35).
Attention! Do not insert the screwdriver too far to avoid damaging the stator winding.
Attention! It may be difficult to remove the alternator rear bracket because the circlip used to secure the rear bearing is in the way. To facilitate rear bracket removal, heat the bearing assembly with a 200W soldering iron.
Attention! Do not use a heat gun for heating, as this may damage the rectifier diodes.
Secure the rotor in a vise with the pulley side up.
Attention! Make sure the vise jaws do not damage the rotor.
Pic. 7.36. Removing the alternator pulley
Unscrew the pulley fastening nut, remove the spring washer, then the pulley and spacer (pic. 7.36).
Remove the alternator front bracket and o-rings.
Remove the rotor from the vise.
Pic. 7.37. Places for soldering contacts to the rectifier unit
Before disconnecting the rectifier unit from the brush holder, unsolder the two contacts (plates), soldered to the rectifier block (pic. 7.37).
Rotor check
Pic. 7.38. Checking the circuit between slip rings
Check for an open in the rotor winding. Check for continuity between slip rings (pic. 7.38).
If there is too little resistance (tends to 0), which indicates a short circuit. In the event of an open circuit in the rotor winding or a short circuit, replace the rotor assembly.
Resistance: Approximately 3.1 ohms.
Check that the rotor winding is not shorted to «mass».
Pic. 7.39. Checking for continuity between slip ring and core
Check for continuity between slip ring and core (pic. 7.39).
If there is a closed circuit (short circuit «mass») replace the rotor assembly.
Stator check
Pic. 7.40. Checking the closed circuit between the stator winding terminals
Check for an open in the stator winding. Check for a closed circuit between the stator winding terminals (pic. 7.40).
If the winding circuit is open (resistance tends to infinity), then replace the stator assembly.
Pic. 7.41. Checking the absence of a short circuit in the stator winding «mass»
Check the absence of a short circuit in the stator winding for «mass» (there is no closed circuit between the stator winding and the core) (pic. 7.41).
If the circuit is closed (resistance tends to zero), replace the stator assembly.
Checking the positive output of the rectifier unit
Pic. 7.42. Checking the closed circuit between the output «positive» diodes of the rectifier unit and the output of the stator winding
Using an ohmmeter, check that the circuit between the terminal «positive» diodes of the rectifier unit and the output of the stator winding is closed (little resistance) (pic. 7.42).
Reverse the polarity of the ohmmeter probes and measure the resistance (if the resistance is small, i.e. the circuit is closed in both directions, then the diode is broken). Replace the rectifier assembly.
Checking the negative terminal of the rectifier unit
Pic. 7.43. Checking the negative terminal of the rectifier unit
Using an ohmmeter, check that the circuit between the terminal «negative» diodes of the rectifier unit and the output of the stator winding is closed (little resistance) (pic. 7.43).
Reverse the polarity of the ohmmeter probes and measure the resistance (if the resistance is small, i.e. the circuit is closed in both directions, then the diode is broken). Replace the rectifier assembly.
Checking the three diodes of the rectifier unit
Pic. 7.44. Checking the three diodes of the rectifier unit
Test three diodes by connecting an ohmmeter to both terminals of each diode. For each diode, the circuit must be closed in only one direction (pic. 7.44).
With no closed circuit in both directions (or if there is a closed circuit in both directions) the diode is faulty and the rectifier unit (heat dissipating block) to be replaced.
Assembly
Assembly is carried out in the reverse order of disassembly. Pay attention to the following:
Pic. 7.45. Fixation of raised brushes
before installing the rotor in the rear bracket, insert a thin wire into the small hole in the bracket to secure the raised brushes (pic. 7.45). Remove the wire after installing the rotor.
Installation
Install the alternator in place and insert the pivot bolt (do not tighten the pivot bolt nut).
Pic. 7.46. Generator installation
Push the alternator forward and determine how many spacers (each 0.198 mm thick) must be inserted between the front strut of the generator and the front cover of the engine (gap «A» in Figure 7.46).
Pick up enough spacers so that they do not fall when you try to insert them into the gap.
Pic. 7.47. Ventilation hole in the battery cover
Insert spacers (into the gap «A» in figure 7.47), connect and tighten the pivot bolt nut to complete installation.