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Keep your alternator in good condition. This page is specifically for the Hitachi LT135 unit.
Contents |
Brush Check
Worn brushes can cause flickering dash lamp, or intermittent charging.
Very easy to check -- these just unbolt from the rear of the alternator. Replace if worn down to the line. Also check the brush pig tail and replace if obviously worn to the point of near-breakage.
Brush comparo:
- Left: worn down to the limit line (7 mm or less)
- right: New
Rotor
After removing the brushes, you can test the rotor (without disassembling the alternator -- by viewing down the hole the brush holder came out of). Or you can disassemble the alternator.
Using an ohmmeter, check between the two copper slip rings:
- Should be around 4.4 ohms (with ohmmeter on lowest range)
- No continuity means the winding is broken or detached
- Lower ohms may indicate a short, perhaps from bad insulation
- Neither condition is easily fixable. Replace it.
Also check for isolation:
- There should be no continuity (even using 1M-ohm scale) between either ring and the rotor metal or shaft (or alternator case).
- If there is, it is shorted. Replace it.
Disassembly
- Remove the brush holder assembly
- Remove the three 8mm-head long bolts from the rear face. You can use an 8mm socket or 5/16" socket.
- Then separate like this:
-
Note that one through-bolt is longer than the other two.
Rotor Maintenance
- Rear Bearing Repack: Carefully pry up a bit of the retainer and pack it with high-temp wheel bearing grease. Then carefully tamp the metal back down.
-
- Clean the slip rings with ether and polish with super-fine (400 or 600 grit) non-ferrite sand paper.
- Wipe off all grease. Carefully remove excess grease from back side of bearing and slip rings.
- The front bearing can be packed in a similar way.
To check if the bearings need changing or packing, spin them. They should be silent, and not spin free which indicate there is no more grease in them. They should turn easily, smoothly and silently.
To get to the front bearing:
- Remove the pulley with a 13/16" box wrench or socket
- Use a large screwdriver in the pulley fins to hold it steady while removing the nut
- After the pulley is off, remove the three screws hold the bearing retainer. Then separate the rotor from the aluminum case plate.
-
Bearings
To replace the bearings, use a medium size two- or three-jaw bearing puller. Alternatively you can use a press.
You may be able to re-lube the bearings (see above Rotor Maintenance section).
Rear Bearing
- NSK 620-1Z (metal retainer) or 620-1V (rubber retainer)
- Timken 202SS
- Timken 201SS
- BCA/NATIONAL 201SS
Specs:
- Ball Bearing Outer Race Radius=0.024"
- Bore=0.4724"
- Outer Diameter=1.2598"
- Width=0.3937"
- Inner Race Radius=0.024"
Front Bearing
- NSK 620-2Z
- TIMKEN 203FF
- TIMKEN 202FF
- BCA/NATIONAL 202FF
- SKF 62022ZJ
Specs:
- Ball Bearing Outer Race Radius=0.024"
- Bore=0.5906"
- Outer Diameter=1.378"
- Width=0.4331"
- Inner Race Radius=0.024"