hi john.
i have had the same problem but with my ABAC compressor you will have to replace your cutout unit as the diaphram is alowing the air to leak through.just type in your model no and make then you can choose from a list of options to look at and see diagrams of your machine.once you have found the right part order it from the manufacture mine cost about £40.hope this helps mate.
roger
July 2008