Thanks for the post L.J.,

It depends on the model (series) Furnas switch you have, actually.

On some models, the Differential screw adjusts the cut-IN pressure while on other models it adjusts the cut-OUT pressure.

Do you have the model# of the switch? It should be on the inside of the plastic cover, or possibly on the cast portion of the manifold.

- MTR

It can be confusing, yes

Your switch's Differential setting adjusts the cut-OUT pressure, which is the 120 PSI specification (max PSI setting).

You cannot adjust the cut-IN pressure separately, unfortunately. However, there should be another adjustment screw for the "Range". The Range adjustment screw will increase or decrease BOTH the cut-in pressure and cut-out pressure simultaneously. Typically this is a larger screw, sometimes plastic.

If you do have a Range adjustment screw, turn it C.W. one turn to see if that increases the cut-in pressure enough.

Remember! This will also increase the maximum cut-OUT pressure, so make sure it doesn't adjust it past the PSI recommended for your compressor.

- MTR