Cummins/Onan — Cooling System - Performance Test
Testing & diagnosis
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan HGLAA
Procedure
- Complete a representative installation.
- Disconnect the AC leads from the vehicle loads.
- Connect the load bank to the AC leads.
- Conduct the test where ambient air temperature remains within the specified range.
- Measure generator set inlet air temperature with a thermocouple tied in the middle of the inlet air grille.
- Measure ambient air temperature with a shielded thermocouple within 1.2 m (4 ft) of the generator set at approximately the same height.
- Measure oil temperature (CAN J1939 or thermocouple).
- Close all compartment doors.
- Run the generator set at full load for at least an hour.
- Record temperatures at 15 minute intervals until they stabilize.
- Stop the generator set and disconnect the load bank.
- Reconnect the AC leads to the vehicle.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Ambient air temperature: MAX 38 °C (100 °F), MIN 16 °C (60 °F)
- Oil temperature must be below 155 °C (311 °F) under all conditions
- Typical oil temperature 122 °C (251 °F) at 20 °C (68 °F) ambient
- Intake air temperature rise over ambient good: 0-5 °C (0-9 °F); adequate: 5-10 °C (9-18 °F); poor: 10-15 FridayParts $30.67 °C (18-27 FridayParts $12.99 °F)
Full service-parts list: Cummins/Onan HGLAA →
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.