Cummins/Onan — Replacing SCRs and CRs
Repair & overhaul · SCRs and diodes
From a Cummins/Onan service manual covering: 300.0 DFT, 350.0 DFU, 350.0 WF, 400.0 DFV, 400.0 WK, 450.0 DFW, 500.0 DFY, 600.0 DWV. Check it applies to your exact model before use.
Applies to: Cummins/Onan YB series
Before you start
- Use a 40 watt soldering iron. Hold a needlenose pliers between rectifier and soldering point to prevent destructive heating.
- Excessive heat on these components will destroy them.
Procedure
- Unsolder leadwires from terminals.
- Use proper size wrenches to hold body while removing nut.
- Push rectifier free of mounting hole in heat sink.
- Insert new rectifier into mounting hole. Secure with nut and washer.
- Torque diodes on rotating exciter assembly to 15 lb-in (1.7 N·m).
- Solder leadwires to new rectifiers.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 15 lb-in (1.7 N·m)
Full service-parts list: Cummins/Onan YB series →
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.