Help needed on Air Compressor

[Apples69]

I purchased a few years ago from Mitre 10 a Chinese made Scorpion Weeken Warrior Air Compressor.
It's a 2 HP / 25 litre tank. Just recently it started to let all the air out of the tank once it hit the target pressure for the tank.
The air comes out if the black box under the on off switch ( little red button on top of black box ) as per listing below
https://www.autobarn.com.au/powerbase-2hp-25lt-air-compressor-pb-02021
My compressor engine is reversed on mine to the photo but on off looks the same
Any one got any idea why this happens

[Coolblue80]

There is a relief port in there. Possibly to relieve head pressure as the compressor starts??? There is also a pressure relief valve which will release at max pressure. The black box you speak of is known as a Condor switch. Usually between $50-$70. The cheaper compressors will have everything assembled into that switch with a glue which tends to be stronger than the metal that the fittings are made of. Hence when you go to pull the fittings out,  they break.
This is of course my take on it. I could be wrong.
Cheers, Mike.

[jclures]

It might be there is a valve on the air delivery line,  normally screwed into the tank. When this valve plays up, it sticks, and in turn the air is then released into the regulator, making it release the air to the atmosphere.
It might look like this.
https://www.ebay.com.au/itm/QUALITY-AIR-COMPRESSOR-1-2-BSP-CHECK-VALVE-NON-RETURN-VALVE-MADE-IN-ITALY/151957395658?epid=1954931784&hash=item23615dd8ca:g:myMAAOSw5dNWoFwQ

[jclures]

You can get them cheaper than this on  on ebay.
For example.
https://www.ebay.com.au/itm/G1-2xG3-8xG1-8-Male-Thread-3-Way-Air-Compressor-Non-Return-Check-Valves-2pcs/332097697284?hash=item4d5290b604:g:uzsAAOSwyP5aS5BX

[Apples69]

Thanks for the replies. The normal relief valve Is fine as pulled this apart and tested. The rest is a PITA to pull apart as need to pull out motor to enable the unscrewing of the black box ( sorry forgot what it was called ).
Got nothing to lose so might pull the little black box apart next weekend.

[corndog]

I could be way off but I thought the black box just housed the electrical components.

[tryagain]

My compressor did similar a couple of years ago but then righted itself, but you can get a replacement "black box" pretty cheap on eBay, probably the easiest way to go.

https://www.ebay.com.au/sch/i.html?_nkw=air+compressor+pressure+switch

[jclures]

I could be way off but I thought the black box just housed the electrical components.

It unloads the air from the compressor (this is to allow the compressor to restart not under pressure) as well as control  the pressure settings

[macca]

It unloads the air from the compressor (this is to allow the compressor to restart not under pressure) as well as control  the pressure settings

JC is on the money, the valve is the pressure cutoff and unloader for motor restarts. They are easy  to replace, two wire's and then just unscrew it from the tank.  There is a screw under the cover to adjust the cutoff pressure, it may have to be reset.
Those wires are 240 volt tho 🤥

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[Apples69]

Thanks Macca - I'll gave a look for a reset screw - if I turn off the main switch before it gets to total pressure it all works fine

[kylarama]

It might be there is a valve on the air delivery line,  normally screwed into the tank. When this valve plays up, it sticks, and in turn the air is then released into the regulator, making it release the air to the atmosphere.
It might look like this.
https://www.ebay.com.au/itm/QUALITY-AIR-COMPRESSOR-1-2-BSP-CHECK-VALVE-NON-RETURN-VALVE-MADE-IN-ITALY/151957395658?epid=1954931784&hash=item23615dd8ca:g:myMAAOSw5dNWoFwQ

JC is right.  If air is coming out of the 'black box' after it shuts off the check (one way) valve in the tank is probably stuck open and emptying the tank via the unloader valve in the 'black box'.  Give the check valve a few 'Technical taps' to see if it frees up. Or unscrew the pipe that feeds from the compressor head. Have peer inside to see if its stuck open.

I'd look at this before the pressure switch.

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[The punter]

New pressure switch, diaphragm is probably hosed, 12 bucks on ebay

[Barrabart]

G'day Apples,

There will be a copper or nylon pipe running to the underside bleed valve on the pressure switch, the other end of this line connects to the non return valve on the air receiver.
You will find that your non return valve is shot, normally a small disc shaped neoprene valve inside the NRV.
What's happening is the bleed valve on the pressure switch is doing it's job, it's releasing the air being presented to it. The problem is if the valve in the NRV is shot, it's allowing air from the receiver to run back out to the bleed valve. The bleed valve is designed to release the air trapped above the NRV, between the cylinder head and NRV.
Pull out the NRV, I bet ya it's stuffed or has something jamming the disc valve inside.

Regards,

Barrabart.

[Apples69]

Thanks everyone - it's funny how there are parts available even though it's only a cheapy air compressor
For ten bucks can't go too far wrong and buy a replacement