Cummins/Onan — Temperature Test
Testing & diagnosis · Cooling system
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan HDKA, Cummins/Onan HDKAJ, Cummins/Onan HDKAK
Before you start
- To prevent severe scalding, always let the engine cool down before removing the coolant pressure cap. Turn the cap slowly, and do not open it fully until the pressure has been relieved.
Procedure
- Conduct this test on the first installation representative of a new commercial application of a Model HDKAT genset.
- Locate a shielded thermocouple in the center of the air inlet opening of the genset to measure inlet air temperature.
- Locate a shielded thermocouple within 48 inches (1.2 meters) of the inlet air opening and at the same height to measure ambient air temperature.
- Locate a thermocouple on the oil dip stick to measure oil temperature. Do not extend past the ball on the end of the dip stick.
- Relieve coolant system pressure by loosening the coolant pressure cap. Secure the cap and remove the coolant hose from the thermostat outlet. Secure a thermocouple so the bead is in the center of the
- Run the leads out between the fitting and hose and secure the hose with a new hose clamp.
- Conduct the test where ambient air temperature remains between 60°F and 100°F (16°C and 38°C).
- Connect the genset to a load bank that can be adjusted to apply full rated load.
- Run the genset under full-load, with all service and compartment doors closed, and record temperatures every 15 minutes until they stabilize.
- Temperature is considered stable when there is no change in three consecutive readings.
- To determine temperature rises, subtract the ambient air temperature from the other temperatures in the same column.
- Inlet air temperature rise must not exceed 8°F (4.4°C).
- Oil temperature rise must not exceed 190°F (106°C).
- Maximum coolant temperature is 230°F (110°C), at which point the genset will shut down and fault code No. 33 will be displayed.
Tools required
- Thermocouples not heavier than No. 24 AWG Amazon
- Shielded thermocouple with 2 inch diameter by 6 inch long white PVC pipe or equivalent
- Load bank Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Inlet air temperature rise: max 8°F (4.4°C)
- Oil temperature rise: max 190°F (106°C)
- Maximum coolant temperature: 230°F (110°C)
Full service-parts list: Cummins/Onan HDKA →, Cummins/Onan HDKAJ →, Cummins/Onan HDKAK →
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.