Iwata HP-C Plus and under trigger problem

[Squishy]

@Arron. What exactly is happening after 15 mins? Are your compressor filters full of oil/water, is it possible that any is getting into your air hose? Are you emptying your compressor tank regularly, if its a tiny one you may need yo do it at the end of each session, and if you do empty it frequently is the water looking oily or rusty?
It is possible that you need to replace your air valve spring, it may have lost some of its oomph, or the tiny o ring in there could need replacing. I recently had to do that on my micron, I felt I wasn't getting the right amount of air flow, and when I looked that little o ring was pretty flat. I replaced it and voila, working fine again.

 

[AndreZA]

You do not need to lube anything in the airvalve. On my secondhand HP-B the trigger moved up and down really smoothly but it did not want to work with a softer spring. The little mushroom plug underneath the trigger was fitting just too perfect in the in sleeve. In this case I did try Iwata spraygun lube but it still did not work. I then tried a mushroom plug from an Olympos. Perfect fit and works like a dream with the soft spring. It is obviously a smidge thinner. The good part is the Iwata plug fits the Olympos perfectly as if it was an OEM part. Both guns happy and owner ecstatic.

 

[Ronald art]

I agree with Andre , no need to lube the airvalve , I only did it once after I forgot to remove the airvalve and gave my HP SB+ a deep clean in the ultrasonic and I dont use the superlube as that is bound to give you trouble in the long run as it gums up and makes things worse.
In general I never lube anything on my airbrushes except for the needle but only that little part of the needle that moves in the seal as I like my springs as soft as possible and that means turning the needle spring adjuster as far out as it will go

 

[RebelAir]

In most cases as a few mention their is no need to, except when it freezes LOL, this happens often when people soak their brushes in thinners for too long as it swells the rubber or when paint gets into it. I personally wouldn't use super lube, vaseline is used often in industry to lubricate orings but havent personally used it in an airbrush airvalve, a light pneumatic oil or simple spit is all that's needed. if paint has got in there due to a loose packing nut then occasionally a clean does help and it may have to be disassembled but I prefer not to pull apart the air valve if it can be avoided, a soak in warm water, whilst in its bath simply trigger the pin a few times then reattach it to your compressor and trigger it by pushing the pin up and down a few more times. This should throw out any loosened paint. One drop of pneumatic oil, trigger it a bit more and it will last for ages and not cause any probs until more paint, oring swell or another issue arises with it.