Cummins/Onan — Permanent Magnet Exciter Replacement
Repair & overhaul
From a Cummins/Onan service manual covering: 4BT3.9, 4BT3.9-GC1, 4BT3.9-GC2, 6BT5.9, 6BT5.9-GC1, 6BT5.9-GC2, 6CT8.3, 6CT8.3-GS/GC1, 6CTA8.3, 6CTA8.3-GS/GC1, 6CTA8.3-GS/GC2. Check it applies to your exact model before use.
Applies to: Cummins/Onan 4BT3.9, Cummins/Onan 6BT5.9, Cummins/Onan 6CTA8.3, Cummins/Onan 4BT3.9 engine, Cummins/Onan 6BT5.9 engine, Cummins/Onan 6CT8.3 engine, Cummins/Onan 6CTA8.3 engine
Before you start
- Highly magnetic rotor will attract stator core; avoid contact which may damage windings.
Procedure
- Place dowel pin into locating hole at end of main rotor shaft; tap to secure fit.
- Assemble permanent magnet to main rotor shaft using dowel pin; secure with through-bolt; torque 40 to 45 ft-lbs (54 to 61 N*m).
- Place stator on endbracket with leads at 12 o'clock position; secure with bolts and clamps.
- Route and connect VR21 and PMG leads P2, P3 and P4 to auxiliary terminal block.
- Mount endbell cover with four M5 screws and lockwashers.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Through-bolt torque 40 to 45 ft-lbs (54 to 61 N*m)
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.