Cummins/Onan — Coolant Heater Service
Maintenance
From a Cummins/Onan owner's manual covering: 450 DFW, 450 DM, 500 DM, 600 DFY, 750 DFZ. Check it applies to your exact model before use.
Applies to: Cummins/Onan 450 DFW, Cummins/Onan 450 DM, Cummins/Onan 500 DM, Cummins/Onan 600 DFY, Cummins/Onan 750 DFZ, Cummins/Onan VTA-28-GI engine, Cummins/Onan VT-28-G engine, Cummins/Onan VTA28-G2 engine, Cummins/Onan KTA-38-GI engine
Before you start
- Failure to remove AC power presents a shock hazard and can cause serious personal injury or death.
- Contact with hot coolant can result in severe burns.
Procedure
- Remove AC power from coolant heater.
- Allow heater to cool before proceeding.
- Remove the head and valve assembly.
- Clean any scale deposits out of the tank.
- Remove heating element and scrape off any accumulated scale.
- Restore AC power to heater after system has been filled with coolant.
Source: Cummins/Onan owner's 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.