Strange problem with compressor

[stillp]

I've got an AS-186 compressor, purchased from John a few years ago. It's served me well but has recently developed a strange problem.
If I set the pressure to less than 15 psi, all the stored pressure in the tank bleeds away without me using the airbrush, and the compressor doesn't restart. Above 15 psi it works fine.
Anyone have any ideas?
Pete

[peterairfix]

I have a slightly newer one and mines OK with the same problem it's set a 15 it does restart OK but it's difficult to switch on in the morning.

[adt70hk]

That's odd. But can't help. Sorry.

[Tim Marlow]

Sounds a bit weird to be honest. My old AS 186 didn’t have a reducing valve, so used to pulse annoyingly when in use because tank pressure was only controlled by the limit switch. Filled to about 25, then drained to about 5 before refilling. Maddening!
I may therefore not quite understand the problem. if I have got it wrong then ignore this….
As I understand the problem, the compressor tank fills according to the inbuilt limit switch and you then set the delivery pressure independently using a pressure reducing valve (PRV) fitted on the hose outlet? The air then bleeds out of the PRV until there is nothing left.
Perhaps there is therefore a fault with the pressure reducing valve or gauge? Do you set pressure with the airbrush running? It may be that the gauge is inaccurate (even good ones are very unreliable) and what seems to be a setting of 15psi is actually zero. The pressure would then bleed out of the PRV. Peter’s could be the opposite…15 could be well above the actual limit switch pressure, so the compressor won’t start because the tank is already at pressure?
Just out of interest, have either of you drained the tank and PRV catch pots of condensate recently? Might just be moisture in the PRV or limit switch?

[stillp]

Not quite Tim - my compressor only has the inbuilt pressure limit switch. I drain the air tank regularly, and I've never had any moisture in the catch pot under the pressure switch. Another thing that's puzzled me is that I can't hear where the air is going when it bleeds down from 15psi to zero. Perhaps the problem is in the flap valves in the actual compressor head - more than 15psi holds it shut, less allows it to bleed a little air back?
Pete

[Jim R]

A few years ago I had an AS-186. I saw a video on YouTube showing how to do a simple service. The head is removed and any debris cleaned out and the brass? flap valve was flattened and centered over the hole. I did that to mine, it was easy.
Jim

Video HERE

[stillp]

Thanks for the video link Jim. We used to have a guy on here, Paintguy, who did the same. Having a rethink though, it can't be (just) the flap valve - the compressor doesn't restart when the pressure drops, so it must have a faulty pressure switch.
Pete

[Tim Marlow]

Not quite Tim - my compressor only has the inbuilt pressure limit switch. I drain the air tank regularly, and I've never had any moisture in the catch pot under the pressure switch. Another thing that's puzzled me is that I can't hear where the air is going when it bleeds down from 15psi to zero. Perhaps the problem is in the flap valves in the actual compressor head - more than 15psi holds it shut, less allows it to bleed a little air back?
Pete

Best way to find an air leak like that is a solution of washing up liquid and a paintbrush. Make up the solution, dip in the brush, drain off the excess, and hold the brush on various parts that could leak until you see bubbles…..Savlon is even better. You can paint that on and wait for the bubble beard to form…..we used it all the time to find pin hole leaks on pharma kit……obviously don’t put it on electrical bits though…..

[stillp]

Good idea Tim, I'll try that later.
Pete

[Ian M]

Don't forget to test the airbrush for leaks as well. I discovered mine was bleeding off air very slowly from the nozzle. Must have had a bit of gunk in some place or the other. Gave it a good clean and it was fine.

[stillp]

It doesn't lose pressure - even slightly - unless it's set to less than 15psi though. I usually leave it switched on when I'm not using it - even for a couple of days, and the pressure in the tank stays up.
Pete

[outrunner]

I had a similar problem with mine last year, have a look at my thread here and see if it is any help.

Andy.

[stillp]

Sounds like a similar problem Andy, thanks. The guarantee on mine ran out about 5 years ago though! I've ordered a new regulator now, I found an ebay supplier had them for under a tenner.
Pete

[Jim R]

Hi Pete
Worth a go for a tenner definitely. When fitting it it might be worth giving the whole thing a bit of a service.
Fingers crossed for you.
Jim

[outrunner]

I hope it fixes it for you.

Andy.