saltshaker Posted August 19, 2012 Author Report Share Posted August 19, 2012 My gun is now shooting straight air. No stopping it!!! It'll shoot paint if I pull the trigger back, but, the air will not shut off. I'm guessin' the MAC valve has crapped out? Quote Link to comment Share on other sites More sharing options...
Brent R Posted August 19, 2012 Report Share Posted August 19, 2012 Salt are you pushing the main lever down for air...or is air coming through the gun by itself....if you are not pushing the main lever down it's not the mac valve. Try turning the mac valve and see if the air slows down....i am assuming you have a High Line CH.... Quote Link to comment Share on other sites More sharing options...
saltshaker Posted August 19, 2012 Author Report Share Posted August 19, 2012 Brent, I can turn the air off one of 2 ways: 1. Turn the MAC completely off. (as I open it...the air flow gets stronger) 2. Disconnect the hose from the compressor or the gun. Quote Link to comment Share on other sites More sharing options...
RayburnGuy Posted August 19, 2012 Report Share Posted August 19, 2012 It's not the MAC valve. The MAC valve is downstream from your trigger valve and doesn't come into play until after you pull the trigger to start spraying paint. Sounds to me like you've got some problems with the trigger valve. Maybe a torn or improperly installed o-ring? Ben Quote Link to comment Share on other sites More sharing options...
RayburnGuy Posted August 19, 2012 Report Share Posted August 19, 2012 (edited) Brent, I can turn the air off one of 2 ways: 1. Turn the MAC completely off. (as I open it...the air flow gets stronger) That right there tells me the MAC valve is working properly. That's what it does. Ben Edited August 19, 2012 by RayburnGuy Quote Link to comment Share on other sites More sharing options...
saltshaker Posted August 19, 2012 Author Report Share Posted August 19, 2012 That right there tells me the MAC valve is working properly. That's what it does. Ben Listen up dude, I know enough about airbrushes to know that you..... are probably right. I took the trigger assembly apart and oiled it. The o-ring seemed to be intact. I put it back together and kept pushing down on the trigger. The air flow finally lessened a great deal but not completely off. Think I'm gonna buy a new assembly and see if that fixes it. Thanks to you and Brent for the diagnosis. BTW, it should be clearly obvious that I know very little about airbrushes. Quote Link to comment Share on other sites More sharing options...
mark poulson Posted August 19, 2012 Report Share Posted August 19, 2012 (edited) I find that the air valve gets dirty if I am not careful when I clean my airbrush. If I let the dirty backflush paint water get into the area of the trigger and don't flush it out right away, it dries in there and can make the air valve stick. I've been lucky so far, and a thorough cleaning with acetone has freed up my stuck valve when I've had this happen. I find flushing out the whole trigger assembly with clean water and making sure to drain it back out is the best way for me to avoid this problem. Since I've switched to the "total immersion" style of airbrush cleaning, where I hold the airbrush tip and cup underwater in my cleaning tupperware full of clean water while I clean and backflush it, I haven't had that problem. Whatever dirty water makes it's way into the trigger area is cleaned out by the shear volume of clean water that's flushed through the entire brush. I still remove the needle and wipe it clean, and runs some water with dishwashing liquid through the brush after I've done the major backflushing, just in case anything is still stuck anywhere, and I backflush with acetone every so often, if my airbrush seems sluggish. Edited August 19, 2012 by mark poulson Quote Link to comment Share on other sites More sharing options...
Hokieangler Posted October 24, 2012 Report Share Posted October 24, 2012 Maybe your tip may have a hair line crack in it. Quote Link to comment Share on other sites More sharing options...
gunnie3035 Posted October 24, 2012 Report Share Posted October 24, 2012 It is the brass plunger thingy. I have no idea what it is called, the valve stem maybe? The plunger is brass and so are the rings-bushings it slides in and out of or rather up and down. After a while they get worn and it begins to hang up and eventually won't spring back like it should. You start to get what I call hang fires where the airflow doesn't shut off and/or won't let air flow through the brush. Basically what I'm saying is the trigger doesn't compresses the valve stem because the valve stem isn't springing back into place like it should. At times it can even get stuck open (stuck in the downward position). It is a complete untit and can only be fixed by replacing the part. I've had this happen on every Iwata brush I have ever owned after a year of hard use. The part is like $55 shipped. I generally toss the brush and buy a new one. However since this is a higher end brush replacing the part is practical. Quote Link to comment Share on other sites More sharing options...
gunnie3035 Posted October 24, 2012 Report Share Posted October 24, 2012 I think what causes it is the amount of finger pressure applied by the operator. I tend to really clamp down the trigger when painting and flushing. Eventually the abuse wears the brass bushing in the stem. However this is just a theory on why I go through a brush or two per year and other can use the same one for years. Quote Link to comment Share on other sites More sharing options...
Skeeter Posted October 30, 2012 Report Share Posted October 30, 2012 Iwata makes wonderful airbrushes. If you have tried the tips above and still have the problem then I would send it to Iwata to have it fixed. Iwatas are expensive guns and a precision piece of equipment. Send it to the factory. They will get it back in working order for you. Skeeter Quote Link to comment Share on other sites More sharing options...
