VACUTEST 116 does not require special maintenance.However, after a long period of use, the suction filter should be examined and cleaned (A dirty filter will cause the gauge to register a vacuum even when it is on but not m operation).
Remove the back cover of the housing and the filter glass, unscrew the filter and clean it.
When suction capacity diminishes, check the diaphragm pump by sealing it directly (vacuum -800 mbar).
Also inspect the suction hose and rapid coupling, as well as the packing motenal of the adapter.