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Compresor help?

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Hi, in need of some help.

I have a Sil-air compressor:


This one without the cover.

As the tank is only 1L and I'm using it with an air gun to clean machined parts I wanted a bigger tank.

So I found a compressor with a broken motor with a view of using the tank.

Then I noticed it has a pressure switch, mine doesn't.

So I wired mine up to the switch and lo and behold it switches on..

Dial wasn't moving though.....🙄

Hear and felt air coming out from under the switch, took it apart.

Membrane is fine., all the switch gubbins look fine as well.

The air seems to be coming from the line going from the tank to the switch.

At the switch end it seems to have a plunger, that doesn't plunge (ie close the hole).

The plunger part is not removable and is marked with an 8 (for 8 bar I guess).

Anybody know what such a part is called?

This is what the regulator looks like:


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I think the plunger thing might be some sort of valve that opens once a compressor has built up some pressure.

In which case it will never open as the max my sil air can produce is 5 bar.

Off looking for a substitute then.....

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Not really sure what you call a pressure switch, but the plunger is probably the safety valve that purges the tank if pressure exceeds a certain pressure. The valve is supposed to be closed by default until the pressure exceeds 8bar (judging by the big red line on the pressure gauge). If it's stuck to open it's probably defective and needs replacing.

What I would do is remove the entire thing and keep just the secondary tank. Remove the part with the pressure adjustment/pressure gauge/filter from your current setup. Connect the secondary tank to the compressor and add the part to the second tank (on the output, obviously). That way you'll keep the pressure adjustment and more importantly you'll have the factory settings for the actual compressor (starting pressure and stopping pressure). 

However: you need to keep in mind that purging massive amounts of air (like an air gun does compared to an airbrush) causes massive condensation in the system. These compressors aren't designed for that and the filter will most likely be unable to cope. Also: make sure the secondary tank has a valve underneath so you can drain it often (preferably after each use).

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  • 1 month later...

I have given up on using a mechanical pressure switch, as apparently the flow rate is too low to make them work.


the dataplate on the compressor states 5 bar, so i'm guessing I'd need an electrical switch that turns off at 5bar and back on at 3 maybe?

not expecting to muse the airbrush at more then 2.5bar.


having a hard time finding something for such low pressures....any tips?

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Just grab an ordinary one from a hardware store. They state some basic thresholds (like 3 and 6 maybe), but you can play with the internals (there's 2 or 3 adjustment screws in there) to get the start/stop you want. I had to do that for a friend recently, it takes about a half hour of twisting and turning, but it works.

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