Cummins/Onan — Alternator Checkout
Testing & diagnosis · Battery charging alternator
From a Cummins/Onan service manual covering: DL4, DL6, DL6T, DL6U. Check it applies to your exact model before use.
Applies to: Cummins/Onan DL4, Cummins/Onan DL6, Cummins/Onan DL6T
Procedure
- With engine running, check battery charge rate DC ammeter.
- Ammeter should show slight charge tapering to zero as battery becomes charged.
- If constant discharge or high charge, stop set and check drive belt, terminals, leads.
- Measure alternator output voltage: positive lead to output terminal, negative to ground.
- Nominal output voltage should be 13.8 to 14.8 volts.
- If over 15 volts, check voltage regulator leads; replace regulator if shorted.
Tools required
- voltmeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 13.8 to 14.8 volts nominal output
Full service-parts list: Cummins/Onan DL6 →
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.