Cummins/Onan NH-MS/1 / NH-S/1 — Flywheel Alternator Regulator-Rectifier Test
Testing & diagnosis · Battery charging system
For the Cummins/Onan NH-MS/1 / NH-S/1, from the Cummins/Onan service manual.
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Before you start
- Never reverse the battery leads.
Procedure
- Connect a voltmeter across the battery.
- Start the engine and operate at 1800 to 3600 rpm.
- The voltmeter should read 13.4 to 14.05 volts.
- If it does, no further testing of the charging system is necessary.
- If not, install a new regulator-rectifier and retest.
- Be sure it has a good ground connection and the connector is properly seated.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 13.4 to 14.05 volts at 1800 to 3600 rpm
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.