Cummins/Onan — Restoring Residual Magnetism
Repair & overhaul · Shunt field F1 / CR1 bridge rectifier
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan MCCK
Before you start
- Observe diode polarity.
- Insulate bare wires and connections.
Procedure
- Remove the generator end bell wrapper and locate the CR1 bridge rectifier on the top brush holder.
- Make a jumper lead with a 12-ampere, 300-volt diode and a 20 ohm, 10 watt resistor in series.
- Connect the diode end to the genset B+ terminal and the resistor end to the positive (+) terminal of bridge rectifier CR1 for 5 seconds maximum.
- Remove the jumper lead connections and test genset operation.
- Replace the end bell wrapper.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 12-ampere, 300-volt diode
- 20 ohm, 10 watt resistor
- Maintain connection for 5 seconds maximum
Full service-parts list: Cummins/Onan MCCK →
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.