Atlas Copco GA22 will not load

Questions & AnswersAtlas Copco GA22 will not load
Cas Staff asked 4 years ago

Good day Sir!

We got trouble to our air compressor atlas copco GA22+, the air compressor run but doesn’t compressing the air even though at stage of auto loaded, we already replaced the solenoid valve and unloading valve and we checked also the loading valve, but the problem still exists, any suggestion thank you and more power.

Ps. We try to put some valve at flexible hose leading to unloading valve, the working air compressor works when we close the valve little bit, and when we try to fully close the compressor continue to build up pressure even though at stage of auto unloaded, and i observed the oil level goes down when pressure inside of air separator increasing.
Any suggestion will be much appreciated. Tnx

7 Answers
Cas Staff answered 4 years ago


Great to see a marine engineer here, I am one myself too 🙂

You are searching in the right direction, there is something wrong with the loading/unloading of the machine. And installing the extra valve was a great idea!

Depending on the year/model of the GA22, there are two types of unloader valves used.

type 1) the model with the big spring inside it: control pressure applied = unloader valve opens. No control pressure = unloader valve closes. This is the most common in all Atlas Copco screw compressors.

type 2) the model without the big spring inside it: control pressure applied = unloader valve closed. No control pressure = unloader valve opens.

From your experiment with the extra valve installed, it looks like you have a ‘type 2’ unloader valve. Closing the valve means no control pressure, which means the valve opens and the compressor runs ‘loaded’.

So, it seams that the inlet valve itself works OK. You have control pressure, which is OK. Only thing left is the solenoid valve and the pilot ‘loading valve’.

I have attached a picture of the workings of the unloading valve.

number 1 is supply of control air pressure (you installed an extra valve here).

Y1 is solenoid valve
UV is unloading (pilot) valve

UNLOADED condition:
– No electrical power to Y1 solenoid
– UV moves upward
– Compressed air enters chamber “2” and pushes the main valve closed.

LOADED condition:
– Electrical power to Y1 solenoid
– UV moves downwards
– No pressure at “2”
– Main valve opens.

In your compressor, the solenoid valve Y1 is not powered for some reason. Therefore it stays in UNLOADED condition.

Check with a multimeter if you have power at Y1 when loaded, and no power when unloaded. If yes, check the solenoid coil, it is probably burned.

If you don’t have power, check the cable. Check at the control panel connector if you have power over there. Also, check for a bad connection on this connector.

If still no power at Y1, there is probably a bad RELAY inside the controller.

The connection for solenoid Y1 is located at connector X104, pin 1 and 3 (with ‘Electronicon 1’ controller).

If you have a different GA22 version, the connector numbers are different.

Alright, this answer is very long already 🙂 Hope you are able to fix this compressor now. Good luck and if you have any more questions, just let me know.

Cas Staff answered 4 years ago

Mr. Cas,
Thanks for the technical supports..i an also facing the same problem of compressor…
and going to try according your line..

Hope will fix it..

Best regards,

Patrick Whowha answered 5 months ago

Please, where does the control pressure come from? Assuming my compressor is off and i want to start it, where does the control pressure comes from.

Patrick Whowha answered 5 months ago

As per the above air compressor problem of not loading, what you need to do is to check if your solenoid on the unloading valve gets enough power supply when the compressor is started for loading operation. There is supposed to be power supply to the solenoid when the compressor is started for loading operation to open the inlet valve for air to go in and when the compressor has reached its cut off pressure, then the power also cuts from the solenoid while the motor continue running.. You can also remove the solenoid and check by reading the coil and also testing it outside to confirm that it has good magnetism or weak magnetic force. If the solenoid is bad you will have the above problem of the compressor not loading.

Also, you will have same problem if the inlet valve spring is weak or bad as well as other kitting items like seals inside the unloading valve, so it will be advisable that you re-kit the unloading valve.

You should also be aware that if the minimum pressure valve (MPV) located on the top of the separator or air receiving tank is bad, may be due to weak or failed rings and seals, you could likely have similar problem and air returning back into the compressor., and it is advisable that when re-kitting the unloading valve, you also re-kit the mpv valve too.

You may remove the additional valve installed, because your unloading valve must open very well to allow the compressor to load at its rated capacity else you will be causing more damage to the unit and it will not serve your purpose.

Best Regards

Patrick Whowha

gavin answered 3 months ago


I have opposite problem. Ga7ff. when I turn on compressor, state is unloading, solenoid is not activated but air pressure starts to build up. After a few seconds the state goes to loading, solenoid activates and no air coming out top of solenoid. Pressure builds up to 106psi then state goes to unloading, solenoid is deactivated and air comes out top of solenoid. But air pressure continues to build up until 135psi then safety valve blows.

I have checked everything.  Replaced unloaded valve 3 times. Solenoid 3 times.

What could it be? I can’t find any information about a problem like this if unloaded valve is not the issue?

Please help.

ravi answered 3 months ago


to solve your problem replace new unloader kit, and also check whether your are placing the solenoid valve in proper position. fixing the solenoid valve in wrong direction results in loading even after auto unload.

reply if the above procedure works.

Senzo answered 2 months ago

Why do we find oil inside  the air filter and why my air outlet saneloid valve isnt energised at all

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