Cummins/Onan — Flashing the Field (With Generator Set in Operation)
Repair & overhaul · Exciter field / VRAS-2
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Before you start
- Do not maintain field flash connection to exciter circuit longer than 5 seconds; incorrect field flashing can damage regulator.
Procedure
- Start the generator set and operate at normal r/min.
- Touch the positive battery lead to TB1-9 of VRAS-2, and the negative lead to TB1-10.
- Hold the leads in place just long enough for voltage to build to the normal operating level, then remove the leads.
- Check generator voltage, and shut down generator set.
- Restart generator set and run at no load; unit must build up voltage without field flashing.
- If not, shut down and perform continuity check of all related wiring.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 6-volt battery and 12-ampere 300-volt diode; 3-volt source will also work
- For 12- or 24-volt SinoCMP $247.50 source use a 2-watt, 20- or 40-ohm resistor in series with the diode
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.