1. Check line voltage. Robinair VacuMaster® pumps are designed to start at +10% line voltage (loaded) at 41o F (5° C). At extremes, however, switching between the start and run windings may occur.

1. Verify the oil is not a residual accumulation from spillage, etc
2. If leakage exists, the module cover gasket or the shaft seal may need to be replaced. If leakage exists in the area of the oil drain plug, you may need to reseal the plug using a commercial pipe thread sealer.

1. Confirm the vacuum gauge and all connections are in good condition and leak-free. You can confirm leakage by monitoring the vacuum with a thermistor gauge while applying vacuum pump oil at connections or suspected leak points. The vacuum will improve briefly while the oil is sealing the leak.
2. Verify the pump oil is clean. A badly contaminated pump may require several oil flushes. See OIL CHANGE PROCEDURE. Note: Use only high vacuum pump oil such as Robinair’s Premium High Vacuum Pump Oil. Other oils will prevent pull-down to a deep vacuum.
3. Verify the oil is at the correct level. For maximum pump operation, the oil must be even with the OIL LEVEL line on the sight glass when the pump is running. See OIL CHANGE PROCEDURE. Do not overfill — operating temperatures will cause the oil to expand, so it will appear at a higher level than when the pump is not running. To check the oil level, start the pump with the inlet capped. Check the oil level in the sight glass. Add oil if necessary.

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