Compressor cuts out but still air leaking in the pressure switch until it cuts in again..

i suspect that the start/run capacitor is faulty or the centrifugal switch in the back of the motor is faulty

have an accredited electrician check the motor , capacitor and the pressure control switch
the air leak at the head is a faulty non return valve in the compressor line to the tank
available at good tool shops for around $60.00

Hello, You need to check how much Low end pressure you have. The Low pressure cutoff switch will disconnect the compressor if the pressure is too low. The high end pressure switch will do the same thing for extreme pressure.

Sometimes the Low pressure switch will get weak and cut off the system too early. Just change this switch which will come out with only a slight puff of Freon being lost. You can jump the connector with a U shaped wire and bypass the Low pressure cutoff switch. If the compressor works better and does not cut out, it can still be low on Freon or have a bad Low pressure switch.

However, if the compressor cuts out a Second time with the Low pressure switch bypassed, the system is probably overcharged and the HIGH pressure switch is cutting off the compressor. You need to purge some Freon out of the system if High pressure is indicated.

Where it gets tricky is the Compressor will compress both Freon and Atmospheric air. Your efficency drops when the Freon is displaced by Atmospheric air. You will need to find the leak in the system which is allowing Freon to leak and outside air to enter the system. You will get a pressure reading with any gas in the lines.

There are Leak detectors and sealers for the system. I hope you just have a bad low pressure switch which is the easiest solution.

check the refrigerant level. The compressor is running until the low pressure or high pressure switch switch cuts it off.

Running the unit without enough refrigerant will damage the compressor because the lubricating oil is dissolved in the refrigerant. This is the reason for the low pressure switch cut off--to protect the compressor from damage.

If pressure gets too high, the compressor seals will blow. Thus the reason for the high pressure switch. Too much refrigerant or too much air in the system (due to a leak) will cause high pressures.

If refrigerant level appears to be correct, then suspect trapped air from a leak causing a high pressure cut-off. If refrigerant is low, suspect a leak causing a low pressure cut-off.

It could be that there was more than one leak and the dealer found only one. The AC system has two pressure switches to protect the compressor from damage---a low press. switch cuts off the compressor when there is not enough refrigerant in the system, the high switch cuts off when pressures get so high they could blow out the seals. Both are a result of a leak--refrigerant leaks out and air can leak in. Air will compress and when it does, it gets hot--so no cooling, and pressures go way up. So the compressor may have been stopped by those protective switches.

Of course, there could be a bad relay or other circuit malfunction.

Another possibility is that the compressor sat too long before being repaired (but we are talking about weeks going by here, not days). The air and moisture (humidity) that leaks into the system during this time creates acids that will attack the metal reed valves in the compressor. On restart, the damaged metal valves eat themselves in short order. If this is the case, the compressor ran until it seized and will need to be replaced. This particular problem is impossible to diagnose. So the dealer may have done his best.

There are two valves in play here. There is a relief valve that opens when the motor kicks off to release the pressure in the compressor itself. That is normal, and is required so that the motor can restart next time without having to overcome that pressure. The other valve is the problem. It is a reed valve between the compressor and the tank. This valve's job is to prevent the air in the tank from returning to the compressor. Think of it as a ratchet for the air. It is this reed valve that has failed.

hi there, if there is enough air pressure present in the compressor the motor will stop,the pressure switch is working.if there is a good pressure at start then suddenly lost the pressure,there is no maintaining pressure to use but on the pressure gauge appear to be have a good or enough air pressure. check if the pressure gauge have enough air pressure the motor is stop,meaning the cut out limit switch stop the motor,if you loosen the air pressure from the valve until the cut in pressure attain or meet the motor will run again there will be a cycle process of differential pressure of cut in and cut out set up on pressure switch. checking the compressor,be sure there is a high pressure on compressor and the compressor motor is stop,shut off service valve and disconnect unit device / tools from the service valve. if the compressor have enough air pressure crakc down the service valve and observe the pressure until it run again the compressor motor,if the pressure maintain the pressure you need to clean the bench, the problem is the unit device/tool you use is defective, but if the maintaining air pressure in the compressor is lost due to malfuction of motor and the compressor engine. check the pressure switch, check the motor function by loosening the belt and run the motor w/o the compressor engine if it is tripping brought it to service center, check also the lubricant oil,if neccessary change oil.have a nice day and fix my rate thanks a lot.

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--

hello,
well,you have to release the pressure,the cut out pressure at 120 psig.reached,and the cut in pressure maybe at 40 psig.so after realeasing pressure at cut in the compressor will run.if the compressor not run at cut in or after releasing check your power supply if still have,swicth off power breaker,by pass pressure switch,by disconnecting the line on terminals of pressure swtich,connect the line w/out pressure switch
the wire line should supply the the compressor,
open the service valve of compressor,switch on
observe if compressor run and develop pressure or air is coming out to nozzle,if that so switch off again and replace pressur switch.you have defective pressure switch,regards rate me,thanks

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

mine does the same damm thing , is it broke or can it be adjusted . It buggs the heck out of me.