I'm not aware of any maintenance requirements for the pressure switches. If adjustable has it been adjusted outside of it's optimal/design range. Has vibration changed the adjustment?

For operating a motor starter I have one of these on my compressor, it has given no trouble, is adjustable, and seems more rugged than some switches.
http://www.ebay.com/itm/Square-D-Pr..._DefaultDomain_0&hash=item23442f2141


•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-