Airman PDS70S Screw Compressor

[RM Snipe]

Hi all, bought a cheap compressor on weekend at auction when I got it home & started the engine revs high then drops a bit with no air delivery ? Has a start/run unloader switch but no change cycling it.. Read post below (sullair) so went looking for a bell housing inspection plate but is none but it has a hole with no eye access so used phone to take pic of it & looks ok. Started it & took pic & everything seen through hole was spinning..If I turnover engine pulley I can feel coupling spin so could be key is sheared in the air ends metal gear if rotors aren't spinning ? Thought rubber outer gear would give first ? Should it sound like a supercharger while running loaded or not because I just hear a diesel running ? Lifting the lid off box tomorrow so I can see/access air end & take something off to view rotors when turning over by hand.. Cracked oil drain & a bit water than oil came out, oil is clean no metal etc.. Oil level seems to go down a bit then back up with it running for 60sec or so.. On shutdown I can just hear air bleeding somewhere for 10-20sec only like 5psi.. Anything else I should check first Guru's ??

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[RM Snipe]

Hi All, I fixed it was the unloader valve, poppet brass center bolt was stuck in bore, thought diaphragm was stuffed but has no holes & all works now.. Should the diaphragm be flat on both sides & has just deteriorated from suction & oil ?

 

[Queenslander]

I can’t tell you anything about the internals of the compressor but most of the characteristics you describe sound normal.
Most of the gear we run through 1/2 inch hose doesn’t draw enough to load it up.
It’s only when using a 1inch hose that it runs at full revs.
We bought ours from Blue Diamond in WA.. they could probably help you out if you’re chasing parts.