Cummins/Onan — Alternator Disassembly (PTO and Two Bearing)
Repair & overhaul · YD PTO / Two Bearing alternator
From a Cummins/Onan service manual covering: 15.0YD-3G, 20.0YD-3G, 20.0YD-5DG, 25.0YD-3G, 25.0YD-5DG, 30.0YD-3G, 30.0YD-5DG, 6.0-3CS1, 7.5-3CS1. Check it applies to your exact model before use.
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Before you start
- Do not set stator down on open end, top or bottom; stator weight can damage windings.
- Use care to prevent damage to the fan blades.
Procedure
- Disconnect engine PTO shaft.
- Remove control box cover.
- Disconnect alternator output leads from control components.
- Disconnect exciter leads F1 and F2 at printed circuit board.
- Remove control box from alternator.
- Raise end bell end to a vertical position and support unit.
- Remove four nuts from rotor-through-studs.
- Remove end bell by tapping upward around joint.
- Remove four stator through-studs with vise grip pliers.
- Lift stator assembly from gear case adapter and set on its side.
- Remove air baffle by loosening four locking screws.
- Remove rotor and fan using a hoist and rope sling.
- Loosen nut on rotor-through-stud bolt.
Tools required
- hoist and rope sling Amazon
- stator handling tongs Amazon
- soft-faced hammer Amazon
- vise grip pliers Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Source: Cummins/Onan service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.