Cummins/Onan — Battery Checkout
Maintenance
From a Cummins/Onan service manual covering: MDL3, MDL4, MDL6. Check it applies to your exact model before use.
Applies to: Cummins/Onan MDL3, Cummins/Onan MDL4, Cummins/Onan MDL6
Procedure
- Check charge condition of the battery with a hydrometer.
- Electrolyte specific gravity should be about 1.260 for a fully charged battery at 80°F (27°C).
- Add distilled water to keep electrolyte at proper level and recharge the battery.
- If battery will not recharge, replace it.
Tools required
- Hydrometer Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Electrolyte specific gravity about 1.260 at 80°F (27°C)
Full service-parts list: Cummins/Onan MDL3 →, Cummins/Onan MDL4 →, Cummins/Onan MDL6 →
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.