Cummins/Onan — Testing Field Flash
Testing & diagnosis · generator field
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan MDKB, Cummins/Onan MDKBH
Procedure
- Disconnect the governor actuator leads to keep the engine from starting.
- Measure output voltage while cranking.
- If output voltage increases at least 1 volt while cranking, the field excitation system is probably in working order.
Tools required
- voltmeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Output voltage increase of at least 1 volt while cranking
Full service-parts list: Cummins/Onan MDKB →, Cummins/Onan MDKBH →
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.