I'm having some trouble with the air compressor controls in this building. I have two Square D pressure switches, a lead and a lag, that operate a Furnas alternating relay. The way this is wired is, the lead switch operates the alternating relay. The lag switch will help to take up slack, or, if the alternating relay fails to operate, will make both compressors run at the same time.

Now, to the meat of the problem; as we near our pressure set point, the contacts on the lead pressure switch will begin to chatter. This, in turn, causes the alternating relay to chatter, which also causes the motors to both try to run. The pressure switch is not mounted directly on the tank, but on a device (see pics below) which also has the compressor discharge attached to it. What I would like to know is, could this device be allowing the pressure from the discharge of the compressor to affect the contacts of the pressure switch. Also, I haven't had a chance to explain all of this to my boss, so could any of you explain what this device is? I apologize for being long winded, but I want to provide as much info as possible to get the best response.

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