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I've dusted off my Air Pro Tools PS900 and after having cleaned it thoroughly I've run into a weird problem.

When I depress the trigger air goes back into the paint pot and bubbles up through the paint! Luckily I have just been testing it out with water or I might have had a serious mess to content with.

Any advice on this problem am I missing a rubber washer near the main nozzle assembly or something? I don't remember there being one there, but the airflow is definitely feeding back into the cup somehow.

I remember it came with 2 needles and 2 nozzles, so I may have mixed those up, could that be the problem One of my needles is long gone and my other nozzle is toast after a mishap with disassembley

Sounds like it's blocked at the end.

 Thamor wrote:
Sounds like it's blocked at the end.

Would be my guess too. I the air can't exit through the nozzle, it will find the next best opening, in this case the paint cup. Try cleaning it again, maybe opening the nozzle with a fine needle or a dedicated airbrush cleaning tool.

Cheers.

I do not have that model myself, however, ss said above, the high pressure air will go down the paint tube if it can't get out of the nozzle.

By logic, your nozzle is blocked. It could be dried paint or because the needle is the wrong fit.

As well as cleaning it, get hold of the manual and check the needle and nozzle options for that model.

If your tip is able to be removed, put it mineral spirits for a few hours, and carefully use a cleaning tool to get the dried paint out.

Thanks for the suggestions guys! I think my own ignorance of the inner workings of an airbrush might be to blame.

I am able to get paint to spray out of the nozzle at what looks like a good rate.

When I depress the trigger, but don't pull it back, air is supposed to be released through the nozzle around the needle correct? I don't see any way for air to come out of the brush other than the nozzle.

When I pull the needle back it opens up the contact point between the cup and the nozzle correct?

I'm soaking my nozzle assembly in mineral spirits to see if I can get any more bits of dried paint out. It could be that I need to bring the needle back a bit from the nozzle, possibly the needle is not sized correctly for this nozzle, they didn't include a diagram showing how to line the needle and nozzle up :(

You have got a double action brush, which is the good kind.

You press the trigger down for air, and pull it back for paint. The more you pull it back, the more paint comes out, as the needle is pulled out of the nozzle.

People generally adjust the air pressure at the pump and press the trigger full down.

As others have stated, it's likely your nozzle is blocked.

If possible, use an ultrasonic cleaner (sounds expensive, but actually not!) for an excellent, easy and quick solution!

Its not possible that its blocked- thats the only explanation for air coming out of the pot.

When you cleaned it- did you disassemble it, or use any solvents? As the only reasons I can think of for the problem you describe with the info given is improper reassembly, or a harsh solvent was used and it melted the o-rings.

I don't remember there being one, there were 2 nozzles that I used to swap out quite often, each should have had a ring in this case, but neither do now.

I wish I could find the exploded diagram of this AB for reference but haven't been able to so far

Try back flushing it. Half fill the cup with water, then cover the tip of the brush with your finger (careful not to prick yourself on the needle) and use the airbrush. Both actions (press and pull).

If no good...

Have you completely disassembled the brush? If so, check to see if you have properly reassembled it.

Have you checked each piece for paint build up?

If the nozzle is removable check if you can see through it (hold it up to the light). You may need to purchase a reamer to remove build up if this is the problem.

Hi, actually i had the same problem with a cheap badger like Chinese airbrush. the problem there wasnt a blocked nozzle but rather that the seal between the airbrush body and the nozzle was leaky therefore the high pressure air leaked into the paint channel and back into the paint cup.
im not familiar with the layout of your airbrush but all airbrushes i had, have the airflow around the nozzle. therefore if the nozzle is blocked there cant be air back flow because it would have to go trough exactly this now blocked nozzle. if however the air distribution hole surrounding the nozzle is blocked you might get the same problem. that is because then no air can escape the body of the airbrush and it goes trough any possible leaks in the nozzle-body seal making this practically the same problem as the one first described....

i hope it is possible to understand my ramblings ^^ a bit difficult to explain this without diagrams

p.s. nearly forgot the solution ^^ if the air hole is blocked or partially blocked take a toothpick, stick it in and twist it carefully. solvent might help. if the nozzle seal is the problem disassemble the nozzle inspect the seal (rubber or plastic?) replace if necessary or try to tighten the nozzle a bit. dont over tighten because that leaves you easily with a broken nozzle. also if you havent used the airbrush in a while or used solvents for cleaning it is very likely that the rubber / plastic seal got brittle and that cracks allow air to flow back into the paint channel

hope that helps
regards
alex

Or your o-ring seal at the nozzel is bad (if it has one).

best of luck

Thanks for all the suggestions guys!

'm starting to think it's the seal between the air flow and the cup, I will try to solve it with some plumbers tape, it's definitely not clogged anywhere, anymore.