Pulsating Airbrush Problem

I have only seen the pulsation you describe when a needle seal is really leaky.  But, you've changed yours already.  You don't say whether your Paasche is siphon or gravity fed.  If it is siphon, try sprayin it upside down.  You can do this by putting  a piece of tape over the little hole in the bottle lid, removing the tube inside, and filling the bottle with water.  If the pulsing goes away, then the problem is probably something breaking the vacuum needed to draw paint up.  The needle seal is the usual culprit, but any leak in the paint path could cause it.  A poor fit between body and cup might do it.

If you have a gravity fed, or the pulsation didn't go away on a siphon, have a close look at the nozzle.  The nozzle should stick out just a tiny bit past the head cap.  If it's flush or recessed it could affect the spray.  A spare nozzle is always a good thing to have and would be worth trying.

I'm assuming the air flow is nice and steady.  I have heard of junk in the air path causing weird problems.   When your replaced the needle seal, did you adjust it for just a slight drag on the needle?

I hope that helps you solve it.  Please let us know if it does.

Don

   Try setting your operating pressure with the brush trigger depressed and compressor running, also how long of hose do you have? USUALLY any length over 6ft, (staight or spiral), suppresses the surge from the compressor however if your pulling from a tank ???? Head scratcher but keep checking and advising we'll get it sorted out.

Hmm;

 When I started to get pulsing in my system I went to a straight compressor with moisture trap and pressure adjuster and guage . I found my pulsing problems were caused by a faulty seal in the fittings between the tank and compressor . It was a pinhole in the tank right next to the threaded fitting hole .