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Re: cut off switch problem
The pressure switch will trip off when the compressor reaches the rated setting (usually 120 ~150psi). If the compressor keeps running untill the safety pops releasing air (usually about 160psi) then the switch is most likely problem. I use SquareD switch from WWW.Grainger.com. However if the compressor keeps running but never pops the safety and only reaching around 90 to 100psi, then you could have several other issues including: leaking fittings (check with soapy water), worn cylinder and piston (on oilfree compressor examine cylinder from below and look for scratches), leaking valves on oil type compressor. Please email with your finding and any questions Good Luck
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First; most repair centers, mine included, are reluctant to instruct users on how to adjust compressor settings because of the dangers of setting levels to high and risking tank ruptures. 15 to 20 psi is considered explosive pressures so when you are dealing with 135 to 150 psi or higher, you have to be able to understand and respect the dangers. Second; if your compressor was working properly and now isn't and no one changed the setting of the pressure switch, it is more likely you need to replace the switch. If the spring or other mechanisms that controls the pressure the switch turns the motor off and on are damaged or broken they need to be replaced. Lastly; at your own risk, most pressure switches have directions inside the cover on how to adjust the cut-in and cut-out pressures. I have never seen one that requires special tools, usually a screw driver or nut drive will turn the adjustment screw. When adjusting the screw, turn the screw in half turn steps and cycle the motor at least twice between adjustments to check where the switch is cutting in and out. If your switch does in fact require a special tool you will have to see if it is something the repair center can sell you or take/ship the compressor to them for repair.
To increase the life of your compressor you will need to lower the pressure setting of your pressure switch, or replace it with new one that will cut-out at 120. Most compressors have the pressure switch set to cut-out at about 125 psi. Lately, I have seen compessors being sold with factory set pressure from 150 to 200psi. Most single stage compressors can easily handle 120 to 125, however higher pressures are pushing the motor/pump to the limits. This is like driving your car at full speed everywhere you drive. Your car lasts many years because for the most part, you are only uning 20 to 40 % of capacity. Problem is that pressure switch is not really designed to be adjusted (factory set) but not impossible. Look for model number of the pressure switch itself and google for more info. If in fact it cannot be adjusted replace it with generic switch at lower setting. The lower the pressure cut-out , longer life of motor pump. Tiny hole in head is an unloader of sorts and helps the motor to overcome head pressure (yes, this method is less efficient than using pressure switch with unloader valve, however cheaper to build).
the setting of your pressure switch has the ability to
control the cut in and cut out of your compressor.unplug the compressor check the pressure switch by opening the cover loosening the bolt nut at the top cover you can see the four set of contactor inside crack the contactor if disengaging to the other side there should be a disengaging of contactor to cut the power supply if defective replace,if it is functioning normally.if it is not defective set this to what you want operating pressure and observe the cut out pressure several times is needed
follow the pressure switch adjustment procedure.have a nice day and fix my rate,thanks a lot.
if the compressor built up a 20 psig and run at 1.5 hrs.then stop.check the pressure switch the differential
pressure cut in and cut out limit.adjust the cut out to the corresponding cut out pressure you want but not exceed to the designed pressure tank..this will be done on adjusting cut out pressure screw mounted inside the pressure switch.follow the instruction on the manuals adjusting pressure switch.the run time correspond to the cut out limit of the pressure switch.
rate my fix if your satisfied thank a lot.
Sounds like the unloader valve is not working properly. The unloader typically is at the end of a tube going to the pressure switch. The unloader is tripped when the pressure switch cuts off. The purpose of the unloader is to bleed the pressure from the cylinder when the compressor cuts off so the next time the compressor cuts on it will be starting in an unloaded condition.
when the compressor cuts off you should hear a discharge of air for about 3 to 5 seconds if the switch is working properly. The unloader can be adjusted if necessary by loosening the jam nuts and adjusting the unloader towards the lever on the pressure switch.
The pressure switch controls the cut-in and cut-out points for the motor. Some switches have a differential adjustment besides the pressure adjustment. The differential controls the spread between cut-in & cut-out, (say in at 80 PSI, out at100 PSI)
PRESSURE SWITCH IS BAD. NOT ADJUSTED CORRECTLY, POINTS ARE STUCK/WELDED TOGETHER OR THE NIPPLE UNDER IT IS CLOGGED. DRAIN PRESSURE AND REMOVE PRESSURE SWITCH. KNOW YOUR UNITS PSI AND TAKE THE SWITCH WITH YOU TO MATCH. IF YOU WANT TO INVESTIGATE FURTHER BEFORE YOU BUY, LOOK IN THE SIDE OF THE SWITCH AND YOU WILL SEE THE POINTS. THEY SHOULD BE TOUCHING WHEN ITS SUPPOSED TO RUN AND SEPERATED WHEN ITS SUPPOSED TO CUT OFF. HOPE THIS HELPS, JODY
bad pressure switch or it is wired incorrectly replace switch and check the wiring or could be out of adjustment you compressor is made for max 125psi should be a screw to adjust on the pressure switch near where the wires are connected back out counter clockwise to lower and see if that turns it off
The pressure switch has snap action contacts that are opened by a diaphragm pushing against a spring mechanism. Unplug the compressor and remove the cover to the switch and look for the contacts. Make sure that they are not welded together from use. Move the on/off lever to see if they open and close. You may have welded contacts or broken mechanism within switch. A factory replacement is expensive, however if you are a tinker-er you can use a lower price generic pressure switch available on ebay. Switches are sold by pressure range, you need a 120#. Fittings may need tweaking. Enjoy