Medea stalls upon start-up

by Michael P
(Las Vegas, NV USA)

Medea Air-Pro2 Compressor

Medea Air-Pro2 Compressor

Medea silent 3-litre bottle compressor, stalls upon start-up

Hi Bill,

I've got an OLD Medea silent Air-Pro II compressor, bought it in 1986. It's been reliable, bullet-proof and flawless for ALL of these years! It didn't get much use during the 90's, and when I use it, it's maybe one day a week, for an hour or two in any given session.

Upon a cold startup (room temperature) it's fine, it starts-up perfectly, cycles beautifully, charging the 3-litre bottle just fine, clicks-off with that little Hssss, and all is good. It holds its air, everything is fine.

As I begin to consume the stored air, it clicks-on as it normally would, but here's where the problem ensues: it doesn't quite click-on with full power, almost seemingly as if insufficient voltage is getting through to the compressor motor. It chug-chug-chugs a bit, struggling to come on with full power, then just quits after maybe 10-15 seconds of struggling to start-up.

I suspect it's electrical, maybe it's merely a pressure switch or its condenser. I just don't know.

Any thoughts? I'm hopeful that with a replacement part, it'll be as good as new. I just don't have the money laying around to replace this thing with a new Iwata-Medea Air-Pro; having been spoiled by a silent compressor all these years, I just can't do a cheap, noisy compressor.

Thanks so much, looking forward to your reply.

Mike in Las Vegas NV

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Sep 10, 2014
It's fixed!
by: Mike in LasVegas

Hi Bill, others —

Took this Medea to a local art supply store (old school art supply at that). The owner loves to tinker with compressors. He cleaned-out some "gunk" which has built-up in the reeds and pressure switches.

It's working like a charm now; sounds like new as it cycles on/off. Holding pressure — all is good.

Sep 08, 2014
All updates on compressor repair welcome
by: Bill

We all look forward to seeing what develops, with your Iwata Medea compressor, Mike.


Sep 08, 2014
Haven't seen a capacitor
by: Mike P in Vegas

Hi Bill,

Thans for your reply. I wanted to attach a few more photos, but couldn't see a means to do so. The photo in my initial post/question shows a short, silver retaining clamp (upper left of the picture) holding a plastic housing onto the side of the cylinder. I believe that's where the pressure release switch is located. No capacitor there. No cap visible where the on/off switch is located either. (at least, no capacitor large enough which remotely resembles the cap used in the "diagnose the capacitor" tutorial).

I'm wondering if the pressure release switch is perhaps dirty, and somehow causing it to fail, but that won't explain why it works on cold/empty start-up. Which takes us back to your diagnosis.

I have this compressor with a local technician, who likes to tinker with old compressors (he runs a local art store and has years of experience with compressors). His preliminary diagnosis is the pressure release valve. I'll keep this thread posted with updates.

Thanks again for your reply, and for facilitating this great website resource!

Sep 08, 2014
Medea silent 3-litre bottle compressor, stalls upon start-up
by: Bill

Mike, I cannot see from the photo, but does the motor have a small capacitor on it?

The reason I ask is that you say the unloader is working, that the compressor starts OK with no load (no air in tank) and cool, but when it's warmed up or hot there may be some binding going on, and the motor has a hard time starting against that heat-caused increase in load on the motor.

Assuming no change in the power supply, yes, I too think it's electrical in nature, and the inability of the motor to start under any load points first to the start capacitor, then to the motor, then to a pump issue.

If there is a capacitor, see the page on this site about how to check that.

Good luck.


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not enought pressure

by wp oosthuizen
(mokopane south africa)

my air compressor is running great but the air pressure remains low even if I close all the outlets
It's a bit difficult offering specific advice when we don't know the make or model of your air brush air compressor.

See the troubleshooting section.

See the page link there about air compressors that run but don't build pressure. Have a look, do whatever checks you can, and then add a comment here with your findings, and your make and model, so that folks can help.



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