Cummins/Onan — Evacuating the AC System

Maintenance

From a Cummins/Onan service manual covering: ES2075s, FS1870s, M11979s, M1976s, M1977s, M1978s. Check it applies to your exact model before use.

Applies to: Kubota 2482B engine

Procedure

1. Make sure the AC hose fittings are secure at the evaporator and at the power unit.
2. Attach a gauge set to the high pressure (HP) and low pressure (LP) sides at the quick connect access valves.
3. Attach a vacuum pump to the center hose of the gauge set.
4. Open the no load fitting on the pump housing, start the pump, open the manifold hand valves and close the no load fitting.
5. Run the pump for five minutes, then close the hand valves and shut off the pump.
6. Observe the gauge readings for a few minutes; if needles move up there is a leak.
7. Check and tighten fittings, restart the pump and repeat the leak check.
8. Run the vacuum pump for an hour to remove moisture from the system.
9. After one hour, verify LP side reaches minus (-) 29 inches Hg and HP side reads less than zero PSI.
10. Close the hand valves.

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.

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