I HAVE ZT30 ATLASCOPCO AIR COMPRESSOR.THE FAULT PROBLEM ON IT NOW IS THAT IT DOES NOT COMPRESS(LOAD) AND DISCHARGE (UNLOAD) AUTOMATICALLY, IT LOADS AND UNLOAD ONLY IF I MANUALLY OPEN THE MANUAL VENT VALVE. SECONDLY IT UNLOADS BELOW THE MINIMUM SET POINT OF 6.0 BAR. IT DROPS UP TO 0.4 BAR WHICH IS NOT NORMAL. I NEED SOLUTIONS TO THIS PROBEM PLEASE.

that's a big unit. Reach out to Atlas Copco technical department direct.

http://originair.atlascopco.com/atlascopconew/contact.aspx

http://originair.atlascopco.com/atlascopconew/industrial/compressors/atlas-copco-ga-45-ff/75ef5d89-fc23-4eca-8c0c-d5a823922470.html

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Sounds like a bad oil seal. If the oil level is too low, it will overheat.

You need to check the head unloader.
Compressed air that is trapped over the piston when the compressor shuts off will be evacuated to atmosphere through the unloader valve, to prevent that compressed air pressure from adding load to the start up of the compressor motor, when the pressure switch again calls for air. For example, the last time you did a sit-up, you may have folded your arms over your chest, or if you are particularly masochistic : - ) , even held a weight to your chest. What you were doing is increasing the load against which your muscles have to work to effect the sit up.
Compressed air, captured in the cylinder after the compressor shuts off, would increase the load against which the electric motor would have to work. It may increase the load too much, and the motor may fail to start, or it may pull too many amps and fry a fuse or pop a breaker in the panel.
When the compressor shuts off, the unloader valve operates, it unloads the trapped air to atmosphere, and that problem is solved.
The unloader valve is plumbed somewhere in the line between the compressor and the compressor tank.
It is often part of the pressure switch assembly. It will, in many cases, be opened by the pressure switch, when the air in the compressor air tank reaches the set point and the pressure switch trips the power supply to the motor off, and at the same time, trips the unloader valve to open.

it is normaly on the bottom of the pressure switch it will have a small tube hooked to it

You need to check the head unloader.
Compressed air that is trapped over the piston when the compressor shuts off will be evacuated to atmosphere through the unloader valve, to prevent that compressed air pressure from adding load to the start up of the compressor motor, when the pressure switch again calls for air. For example, the last time you did a sit-up, you may have folded your arms over your chest, or if you are particularly masochistic : - ) , even held a weight to your chest. What you were doing is increasing the load against which your muscles have to work to effect the sit up.
Compressed air, captured in the cylinder after the compressor shuts off, would increase the load against which the electric motor would have to work. It may increase the load too much, and the motor may fail to start, or it may pull too many amps and fry a fuse or pop a breaker in the panel.
When the compressor shuts off, the unloader valve operates, it unloads the trapped air to atmosphere, and that problem is solved.
The unloader valve is plumbed somewhere in the line between the compressor and the compressor tank.
It is often part of the pressure switch assembly. It will, in many cases, be opened by the pressure switch, when the air in the compressor air tank reaches the set point and the pressure switch trips the power supply to the motor off, and at the same time, trips the unloader valve to open.

it is normaly on the bottom of the pressure switch it will have a small tube hooked to i

Yes, It will cut off when close the discharge valve. This is happen because your compressor encounter there is no load.
You must open the valve to get it loading .
Regards, Jay

Piston air compressors have to unload to permit a restart, the two mot common types are an unloader valve or free air unloaders.

with an unloader valve this system uses a check valve mounted in the discharge line as it enters the tank, when the pump stops this check closes and does not permit the tank pressure to return to the pump. a unloader valve also opens to allow air pressure in the discharge line to vent, this valve is either on the pressure switch or on some models is on the pump, and is a centrifugal type.

Free air unloaders or head unloaders are a set of fingers that hold open the intake valves on the cylinders to permit the piston not to pump air against a head load, and once the pump is running the fingers retract to allow the pump to function as normal.

i have dealt with this problem at work you have a restriction on your air out put and your comp. is doing what is called short cycling

I have worked on many makita compressors and have run-across this problem on a few of them. Your compressor has a check valve that is supposed to hold tank pressure after the switch reaches set pressure. There is an unloader valve built into the pressure switch that releases the pressure in the discharge hose after the unit shuts off. The unloader allows the compressor to restart with-out any pressure in the discharge line. If the brass check valve is leaking pressure back into the system, air will leak out of the unloader valve. Follow the discharge line to the tank and you will see the brass check valve. To test valve for fault, run the compressor till it builds around 80 psi and unplug the unit from the wall outlet. Remove the 1/4" hose connector from the check valve and check for air leaking out of the valve. If it is leaking you can order form www.toolpartsdirect.com. or call the makita 1-800 number. The price is about the same. Good Luck on your repair.

All electric compressors share a basic design with ac power pressure switch with unloader and checkvalve between the pump and the tank. When the pressure switch powers off, it unloads the compressor by releasing the air in the discharge hose. You will notice a small tire stem pin and a lever to engage it somewhere on the pressure switch. If the compressor stops before reaching set cutoff point, the air pressure remains in the discharge hose not allowing the motor to start, thus the hum you hear. Solution is to check for the proper function of pressure switch /unloader, tank check valve (if check valve leaks air back to compressor it will load motor causing hum) and extra measure check capacitor for at least 90% of rated valve. Finally, do not run this compressor with an extension cord, use more hose instead. enjoy

hi mate it could iver be a faulty load solenoid valve or the unloader its self is jaming up inside which means you have to strip it away from the air end and replace all the seals inside or give it to a specialst we are compressed air engineers we could sort it i will leave you a number call us anytime 07958354730 or call 01752 848801 many thanks