Cummins/Onan — Hot Air Recirculation Test
Testing & diagnosis · Genset installation / ventilation
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, Cummins/Onan HGJAC
Before you start
- EXHAUST GAS IS DEADLY! Do not operate the genset when the vehicle is parked indoors or where exhaust can accumulate.
Procedure
- Complete a representative installation.
- Set up a load bank to run the genset at rated full-load or the maximum available load.
- Conduct the test where ambient air temperature remains between 60°F and 100°F (16°C and 38°C).
- Measure inlet air temperature with a thermocouple tied in the middle of the inlet air grille.
- Measure ambient air temperature with a shielded thermocouple within 4 feet (1.2 m) of the genset.
- Close all compartment doors and run the genset at full-load for at least an hour.
- Record temperatures at 10 minute intervals until they stabilize (no change in three consecutive readings).
- Reduce recirculation if the inlet air temperature rise exceeds the requirement.
Tools required
- Load bank Amazon
- Thermocouples not heavier than No. 24 AWG (0.21 mm2) Amazon
- 2 inch diameter white PVC pipe at least 6 inches long (thermocouple shield) Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Inlet-to-ambient temperature difference must not exceed 25°F (14°C)
- Ambient test temperature 60°F to 100°F (16°C to 38°C)
Full service-parts list: Cummins/Onan HGJAA →, Cummins/Onan HGJAB →, Cummins/Onan HGJAC →
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.