Cummins/Onan — Replacing Rectifiers
Repair & overhaul · Rotating rectifier assembly
From a Cummins/Onan service manual covering: 4BT3.9-GC1, 4BT3.9-GC2, 6BT5.9-GC1, 6BT5.9-GC2, 6CT8.3-GS/GC1, 6CTA8.3-GS/GC1, 6CTA8.3-GS/GC2. Check it applies to your exact model before use.
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Procedure
- Disconnect diode lead wire from stud terminal.
- Unscrew diode from rectifier assembly base.
- Apply heatsink compound to underside of new diode; do not apply to threads.
- Insert new diode into mounting hole.
- Torque diodes to 36-42 in-lbs (4-4.8 N-m).
- Reconnect diode lead wire to stud terminal; torque nuts to 24 in-lbs (2.7 N-m).
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 36-42 in-lbs (4-4.8 N-m) diode torque
- 24 in-lbs (2.7 N-m) nut torque
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.