AB> Theres a thought. Semi's come with air reserve tanks as well. But the
 AB> big question is, whats the operating pressure of these systems?
Air pressure range is 0 psi - 120 psi (some are 125 psi).
 DD> There was generally a pressure switch that would not let you release 
 DD> the brakes until you had at least 60 PSI, and the relief valve was 
 DD> around 120.
Not really. It just takes at least that much to start compressing the 
springs in the parking brakes. And on some trucks, the brake valve knob 
won't hold itself in until there is at least 60 psi. The governor 'pops' 
at 120-125 psi. The pop-off valve (pressure relief) goes at 150 psi (or 
there-abouts).
Tom
... I have no solution, but I certainly do admire your problem.
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