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What happened to my compressor and how to fix it ?


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I was working with my compressor today and the airflow adjustment knob has broken off. (see photos)  I have fiddled with it for about 30 minutes but I cannot get the compressor to work at all. That cog will just not turn even though I can push the knob back onto it. Does anybody have any suggestions ?

 

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Before it broke did you need to pull the knob up to change the setting? The big cog isn't supposed to turn in normal operation, it's a locking arrangement. The adjustment will be done by turning the metal spindle in the middle. I note this has a groove in it, looks to me if there's a circlip somewhere in the adjustment knob and its pulled off the spindle. If all else fails you'll probably be able to adjust the regulator by turning the spindle with pliers

Jeremy

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When you say " I cannot get the compressor to work at all" do you mean you are unable to increase the pressure or that the compressor will not run. The components you are referring to are to do with the Pressure Regulator so the compressor should still run irrespective of the setting.

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When you say " I cannot get the compressor to work at all" do you mean you are unable to increase the pressure or that the compressor will not run. The components you are referring to are to do with the Pressure Regulator so the compressor should still run irrespective of the setting.

 

Well, this is where it gets tricky. The compressor should run when it is not connected to an airbrush but it will not. If I push down on that metal part in the middle of the regulator then it will run. I am really not sure what is not working correctly. It does seem odd that both the compressor and regulator should stop working at the same time so I assume (and hope) that only the regulator is broken.

 

This is the type where you pull up on the black knob and turn it to the desired pressure then push it back down to lock it.

 

I looked on the floor and I cannot see any circlip.

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Rather than a Circlip, is there a spring steel wire in the "hood"? It maybe that when pulling up the lock that the hood came off with it. If there is a spring located in the hood (which fits in the groove to retain the hood) it may well push back on with a little bit of pressure. 

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Well, this is where it gets tricky. The compressor should run when it is not connected to an airbrush but it will not. If I push down on that metal part in the middle of the regulator then it will run...

 

That splined metal shaft is turned to adjust the pressure setting. As Jeremy said, the plastic cogs just lock the setting when the outer plastic knob is depressed and release so that it can be turned when the knob is raised. The smaller plastic part sits on the metal shaft and turns the shaft when the knob is turned.

 

Your mention that the pump runs when the metal shaft is pressed down suggests to me that you have managed to completely unscrew the metal shaft so that it is no longer engaged in it's thread (down inside the body of the regulator). This shouldn't happen, but you might try just putting the small plastic part back on the splines and pressing down whilst screwing the shaft in a clockwise direction. I'd avoid using pliers, at least until you get desperate, as they might damage the splines. This way, you may be able to get the shaft re-engaged. If that fails, then it may be that something has failed inside.

 

As others have suggested, there may be an O ring or spring clip inside the small pastic clip, or it might just be a ring moulded inside the hole small plastic part. Whatever, this should only hold the two plastic parts in place and not affect the operation of the valve.

 

I've not stripped mine down, but can confirm that just removing the red ring has no effect. I reckon you would at least need to remove the socket headed plug on the side of the body and, perhaps, also the in and out unions to get inside the regulator.

 

Nick

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The small black piece should be loosely fixed inside the large black knob, and MIGHT be required to somehow spin on it's fixing depending on the design. This applies if the adjuster knob will still spin when it is pushed down to its 'lock' position. If the adjuster knob does NOT spin when it is in its locked position then the small black piece can be permanently fixed into the adjuster knob, as it will never move independently of the whole adjuster knob.

 

Please note the above does NOT account for the up/down movement of the adjuster knob into its 'lock' position. I've completely forgotten how this part works, but it will be simple to work out if you look at it.

 

The small black piece should also be fixed to the silver splined adjuster on the pressure valve, and should not spin on the splines.

 

Fixing is usually a push-fit by way of a circlip, but a U shaped spring clip may also be used. This fixing isn't vital as it's only purpose is to keep the adjuster knob attached to the compressor. In fact this whole fixing can be removed without affecting the operation of the compressor, my old work compressor had the (by now 5 pieces of gaffer taped together-) adjuster knob attached to the compressor leg by a length of string, and was only 'fitted' when adjustment had to be made.

 

Unfortunately this won't explain why your compressor has 'stopped working'. Is the compressor a tank type or a continuous run type? If it has a tank then it should automatically shut off once the tank is full, and only start again once air pressure in the tank gets too low. Does the compressor kick in when air is released? If you turn the silver splined part of the adjuster to fully open, then just spray air from your airbrush, does the compressor kick in?

 

An even simpler test is just remove the pressure regulator completely. Never do this with an expensive airbrush for more than a few minutes, it will damage the seals. But can be done as a quick test to work out what works and what doesn't. Attach the airbrush line direct to the compressor air line - does the compressor now work and provide (quite high pressure) air?

 

Mark

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Well, this is where it gets tricky. The compressor should run when it is not connected to an airbrush but it will not. 

 

Does the compressor run if you take the regulator off? does it run if you bleed the air out of the compressor? If the answer to either of these questions is 'yes' then you need to replace the regulator.

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...Is the compressor a tank type or a continuous run type? If it has a tank then it should automatically shut off once the tank is full, and only start again once air pressure in the tank gets too low....

 

See the photos in the OP. The regulator is attached directly to the compressor cylinder head, so no tank.

 

Your point about trying the compressor without the regulator made me think about Brian's comment that the compressor won't run unless he presses down the splined rod. This might suggest that there is sufficient pressure inside the cylinder to open the pressure switch and cut off power to the motor. Part of the pressure switch can be seen on the other side of the cylinder head on the far right of the last photo in the OP.

 

Pressure can be released from the system by pressing the release valve on the base of the transparent water trap under the regulator. If the pressure switch is working correctly, the motor should run once the pressure is released.

 

Nick

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Buffalo got it right. I pushed down on the metal shaft using the small plastic part and turned clockwise until the thread was engaged and kept turning for a few turns. Everything seems back to normal now. Thank you everybody for your advice.

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Good to hear you got it fixed, Brian. Just to explain the purpose of the red ring that seems to have caused some confusion, it is purely there for panel mounting the regulator or fixing to a bracket as per the pic below.

 

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