Cummins/Onan — Hot Air Recirculation Test Method
Testing & diagnosis · Generator set installation
From a Cummins/Onan service manual covering: 5.5 HGJAA, 5.5 HGJAB, 6.5 HGJAA, 6.5 HGJAB, 7.0 HGJAA, 7.0 HGJAB. Check it applies to your exact model before use.
Applies to: Cummins/Onan HGJAA, Cummins/Onan HGJAB
Before you start
- EXHAUST GAS IS DEADLY! Do not operate the generator set when the vehicle is parked indoors or where exhaust can accumulate.
Procedure
- Complete a representative installation.
- Set up a load bank to run the generator set at rated full load.
- Conduct test where ambient air temperature remains between 16 C and 38 C (60 F and 100 F).
- Measure temperatures with thermocouples not heavier than 0.21 mm2 (24 AWG).
- Measure ambient air temperature with a shielded thermocouple within 1.2 m (4 ft).
- Close all compartment doors and run at full load for at least an hour.
- Record temperatures at 15 minute intervals until they stabilize.
Tools required
- Load bank Amazon
- Thermocouples (max 0.21 mm2 / 24 AWG) Amazon
- 50.8 mm (2 in) diameter white PVC piping shield Amazon
- Temperature recorder Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Temperature is considered stable when there is no change in 3 consecutive readings
- Rise over ambient exceeding 15 C (27 F) must be repaired/modified
Full service-parts list: Cummins/Onan HGJAA →, Cummins/Onan HGJAB →
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.