Cummins/Onan — Zinc pencil inspection (heat exchanger)
Maintenance
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Procedure
- Inspect zinc pencil at least every two months.
- Remove from pipe plug in one end of heat exchanger.
- Replace if deteriorated to less than one half original size.
Specs & values
- Replace when deteriorated to less than 1/2 original size
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.