How do you adjust the on-off pressure settings on this switch?

cut in is about 90 and off is 125 psig yours may not have this differential but set to cut around p90 watch high pressure it should cut off 120-125


Compressor Pressure Switch Adjustment

screws are preset for auto cut off. don't recommend changing screw setting

Remove cap from pressure switch (small nut on top). You will see 3 threaded studs with springs held down by nuts at the end opposite from wired connections. Avoid wired connections with tools and fingers! The center sprung nut adjusts the ON AND OFF pressure settings. Clockwise (tightening down on spring) increases the pressure setting. One of the outside springs controls nothing - note that it has no connection to the switch moving parts. The other one adjusts the OFF setting. So adjust the center one until the ON pressure is 30 psi and then adjust the OFF setting until the pump cuts out at 50 psi. If you have an expansion tank, set this to 2 psi below the OFF setting. (If you have manual for the pump, check the pressure settings in the tables given for your pump.)
If this isn't what you need, please post more info!

Square d recommends that the pressure switch be adjusted to specifications of the particular switch (which is sold in pressure ranges preset at the factory). The switch will be erratic it adjusted out of the factory setting range.
From Square D: (adjust the desired cut-in pressure first, then cut-out)
Cut-in: The large spring controls the cut-in pressure. To make adjustments, turn the nut clockwise (compressing the spring) to raise the cut-in point or counterclockwise to lower the point of cut-in.
Cut-out: The small spring is the differential adjustment and controls the cut-out pressure. To raise the cut-out pressure turn the small nut clockwise (more differential); to lower the cut-out pressure turn counterclockwise.

The best way to go about the task of adjusting the pressure switch is to remove the cover to switch and note the brand/model number. Sometimes instruction are under cover of switch. With switch information, look for mfg. instructions. You will most likely see one or two springs with lock nuts. Do not turn them yet. Most pressure switches are sold with factory adjustment and are sold in pressure ranges. For two stage compressors as yours, the pressure is usually factory set at much higher (150-175) pressures than single stage which is usually about 120 -125. If you change the pressure setting it will also change the differential cut on pressure. The factory will actually use different springs to achieve desired pressures and are color coded. There are too many different brands of switches to recommend how to change pressure setting. You may discover that you can only change the pressure just a small amount (+or -15-20psi ). If you find the information about your switch, make sure that you count the turns exactly so that you can return to factory settings if things go wrong. You can extend the life of the comperssor by lowering the pressure as more amperage /heat is produced to achieve higher pressures. Good luck

That would depend on the type of pressure control switch it had on it, but all of the ones I've ever seen have it near the high pressure adjuster under the pressure switch cover- VERY HIGH VOLTAGES- RISK OF INJURY OR DEATH- UNDER PRESSURE SWITCH COVER WITH UNIT STILL CONNECTED TO POWER-

On the common switch used (A condore mdr 5) the differential is adjusted by DEPRESSING the nob & turning it.

On MDR 4 the adjuster is directly behind the high pressure adjuster. it is a flat bladed screw attached to a spring-screw in to increase cut in pressure.

You can also get pressure switches with a higher cut in pressure.
In Australia from a company called Ross Brown Sales in N.S.W

Hope this helps
Regards Andrew

The adjustment for "Cut-In" and "Cut Out" can be found under the pressure switch cover, if available. Some switches are sealed to prevent tampering that might compromise safety.
If you remove the cover you will see the four electrical connections and one or two screws with springs under them. Most times if the adjustments are accessible you will find a set of instructions under the switch cover. One screw will adjust both the "Cut-In/Cut-Out" pressure and one to adjust the "Cut-Out" pressure only.

However you need to remember some important issues regarding these adjustments. The first is that the "Cut-In/Cut-Out" pressure is set at the factory and is set there for a reason. The only reason to change these is because over time the adjustments can change or you are installing a new switch. The other thing to remember is that the safety relief valve is set just above the "Cut-Out" psi. So any meaningful increase will only trigger the safety valve.

If you need to readjust your compressor back to factory settings make sure you do it with small adjustments. 1/4 to 1/2 turn of the screws. Run the compressor and check both the "Cut-In" and "Cut Out" psi setting before making another adjustment.

Hope this helps, good luck and please be careful.

The pressure switch has an adjustment for the low pressure cut in and the high pressure cut out. If the pressure range is set too close the cycles will be short. You need to work out which setting is wrong by looking at the pressure guage when it is cycling and adjust the pressure switch accordingly.

Hi, W/D here.

To accurately test a switch, it has to be removed from the compressor and tested by raising the pressure and lowering it with air supplied from a known, good regulator. The trip pressures are then noted and adjusted.
The quick and dirty way of "getting close enough" is a little different. Start the compressor, and when it gets to your desired cutoff pressure, pull the plug. Adjust the HP spring untill the contacts trip out. Now, with the compressor still unplugged, drain the pressure off of the tank until you reach your desired cut in pressure, and close the valve. Adjust either the LP cut in or the differential pressure adjustment to set the cut in pressure. The contacts will pull in. If you adjust the cut in pressure with the diff pressure setting, the cut out pressure has to be challenged and set again. Whichever method you follow, you always need to check the upper and lower settings after each adjustment.
Best regards, --W/D--

Generally, the pressure switch is not adjusted more than once or twice in the life of the compressor since the discharge pressure can be adjusted with pressure regulator. However the life of the compressor can be increased if lower pressure settings are maintained. Your pressure switch was set at the factory to a setting of about 120 - 150. If your cutout pressure is higher than 150 surely lower.
STEP 1: Turn Main Calibration Screw ( center screw with large spring) clockwise to increase pressure and turn counter-clockwise to decrease pressure.

STEP 2: Turn Differential Pressure Screw (small spring) clockwise to decrease cut-in pressure and
turn counter-clockwise to increase cut-in pressure.

Differential Pressure is defined as the difference between cut-out and cut-in pressure. There should be about 7 to 12 psi difference between cut-out and cut-in.
In our shop we rarely adjust more than a couple of turns because these switches are sensitive.
Good Luck and please post again if you have other concerns about your compressor.