What's wrong with my air compressor?

[evintho]

Normally, when it cycles it builds up air pressure to about 130psi, shuts off automatically and then gives a pssssssst sound. Now, it builds up pressure to 130psi, shuts off automatically and there's no pssssssst sound. Something is askew! Other than that, everything works fine. I'd like to head off any potential problems.

Also, I just noticed today this white leakage coming from under the cap. Isn't there a condenser under that cap?
It's an I/R 5hp SS5N5. The unit has 101 hours on it. Any help is greatly appreciated!

 

[frankush]

The cap covers either 1 or 2 capacitors that help get the motor turning on startup. Looks like you have a leaker. Fairly cheap to replace.

I don't see a starter, so there should be two capacitors. Before you start messing with them, they'll need a quick discharge. Google it up, very simple to do. Make sure you kill the power first!

The escaping air you hear after the compressor stops, is a good thing. I'm not familiar with the I/R units, but an unloading valve releases the pressure in the cylinders, so that the next time it starts, it doesn't have to work as hard. It may be clogged.

 

[Rookie2]

Yep time for a new capacitor most likely . The pssssssst is the unloader so that the compressor starts up unloaded.

 

[MacMcMacmac]

Any warranty left?

Looks like one of your capacitors is getting ready to pop.

The needle valve on the side of the pressure switch is not being depressed far enough by the metal tab, or there is a build up of sludge from the air going through it which has clogged the orifice. The next time it cycles, have a look at the metal tab that presses on the needle valve. Sometimes you can bend them slightly. Other than that, sometimes the valves work their way loose and back off from the tab. Many are held in place by a very thin nut which can work loose over time. If that's not the problem, the line itself, or the port it attaches to at the check valve may be plugged.

That capacitor needs attention pronto though.

 

[Rookie2]

http://www.surpluscenter.com/shop.axd/Search?keywords=capacitor

 

[james68ssrs]

follow that copper tube to your pressure switch, thats the unloader (check valve) and it sounds like it is blocked, or moved slightly from it's original position. They are usually held in place by a cap screw or similar. remove the tube, remove the check valve and spray some of that wd40 you have on the shelf into it, just move the pin back and forth and make sure it is free. when you remove the check you will see the pin, if not, it is still stuck up in the pressure switch. As for the cap, change it asap. It probably failed because of the harder starting from the jammed unloader check valve, assuming it's the start cap.make sure everything is unplugged and discharged etc.

 

[evintho]

OK, I removed the larger brass valve (I call it a PRV), cleaned it up and sprayed WD40 inside. Opened and closed it several times and it moves freely. Is that the unloader valve or is it a pressure relief valve? Also, what's the one above that with the copper tube running to it? It seems to have an adjustment on it like an automotive TPS. I pulled the tube but it doesn't look like there's any type needle/seat in there. Cleaned it the best I could, put it back together and fired it up. Ran to 130 psi, shut off but no psssst sound.

 

[james68ssrs]

Ok, the big brass valve below with the ring is the safety valve, or releif valve, this is not your issue.The valve attached to the copper tube is your unloader valve, and this is the reason that your compressor is not unloading when it stops. Remove the copper tube and move it slightly out of the way. Now remove the two cap screws, looks like 3/16th hex drive, and slowly remove. You should see a pin inside, this pin is physically pushed when the pressure switch contacts open, or in other words, when the compressor stops. When the electrical contacts open (when pressure set point is reached) the compressor will stop, but also what happens is a metal tab, physically connected to the contact mechanism, pushes on the pin located inside the unloader valve. This will open the valve to atmosphere and vent the compressed air between the head and the discharge check valve, which will be located usually on the tank. All this does is allow the compressor to start again without a head of pressure already in the head. If this small amount of pressure is not vented, then the compressor will labour at start up, which is probably the reason that your cap has blown. Also check the unloader valve for a small vent hole, this is where the head pressure vents, poke a wire in there to make sure it's not blocked, then blow a little wd40 in there first, it might free up, you never know your luck! Failing all of that, remove the pressure switch cover (disconnect power first) and see if you can actually see the tab that activates the pin, all pressure switches do the same thing, but there may be physical differences, I see many different shapes every day, but they all do the same thing, cheers.

 

[evintho]

Thanks for all the help, James! I may have it figured out now. I pulled the unloader valve and cleaned it out really good. When I flip it upside down, the pin slides in and out easily. I threw up a pic so others can see what it looks like. That's a tiny pin! I remounted the valve, fired the compressor and same thing. It shutdown at 135 psi but the unloader valve didn't unload. Next I pulled the pressure switch, located the mechanism that pushes against the unloader valve pin, cleaned it really good, reinstalled the PS, fired the compressor...........same thing! Pulled the PS cover, shutoff the breaker and manually manipulated the mechanism to push the pin in. The compressor unloaded. The small mechanism lever is not pushing the unloader valve pin in. I didn't notice any sort of spring on it. Should there be something or do I have to go for a new pressure switch?

 

[Rookie2]

I'm impressed ! good detective so far ! There is obviously something like a spring or tab or pivot missing or broke. The valve are around 25-$30.00

Supercenter or Ace Hardware

 

[404]

Respectfully suggest you unplug and do not use compressor till the capacitors are replaced.

 

[james68ssrs]

Your welcome. Now that you have located the tab that pushes on the pin, run the compressor normally, but without the pressure switch cover off, and look and see whats actually happening when the compressor reaches set point pressure and stops. As mentioned in an earlier post, the tab may be missing the pin altogether. I also notice some adjustment on the unloader valve, if the pin is not central to the valve body, you may be able to align the pin to the tab with a bit of rotational movement. Just don't get to engrossed with the mechanism when the compressor is still plugged in to the mains, it's still live! If the switch connects and disconnects the contacts,i.e runs, stops, and runs again etc,etc, the spring mechanism that does all of this is ok, the tab is connected mechanically to the contact block, so moves in coordination with the opening and closing of the said contacts. Saying that, the pin should be spring return to close (usually a metal ball, held in place by a small spring against a seat to seal the head pressure, pin is then actuated to push against the ball and opening the head pressure to atmosphere). That ball and spring will be in the main body of the valve, under the teflon piece. The head pressure actually holds the ball firm, the spring just helps relocate it, and the pin unseats it at stop. I agree with 404 senior member 100%, get that cap replaced asap. In nutshell, if the pin is free and moves back to original position after being pushed in, then the tab just needs to be able to connect. If you do not see that tab moving, then yes, I would just buy a new pressure switch and save all the hassle, cheers, James

 

[evintho]

As far as I can tell, when the compressor hits it's setpoint it shuts off automatically but the arm isn't popping up to contact and push in the unloader pin, hence the problem. Just got off the phone with the local compressor shop and he agrees with you. $35 gets me a new pressure switch. I'll be picking up a new capacitor, also.

Quick question. After some youtube searching I learned the capacitor has some sort of bleeddown resistor attached to it. I put a meter on it and didn't get any reading. Is the cap discharged?

 

[404]

Quick question. After some youtube searching I learned the capacitor has some sort of bleeddown resistor attached to it. I put a meter on it and didn't get any reading. Is the cap discharged?

Meter set to DC volts reading zero cap is discharged. Take the old cap with you, there are 2 types possible on motors, run and start.

 

[evintho]

Almost forgot about this thread! Problem solved. Purchased a new pressure switch and now the compressor unloads properly. I had the compressor shop put an analog meter on the capacitor and it checked out good. Also, there was no signs of leakage from it at all. I have no idea where the white chalky residue came from in the second pic but it didn't come from the cap. Must be PFM. Reinstalled the cap and all is good. Thanks for all the help, guys!