Help me replace my air compressor hardware

[MikeH]

Please bear with me. I’ve used air compressors, but I’ve never bothered to work on one. I’ve got one that has a bad unloader, and I’ve decided to just replace the whole manifold, etc., because the old one isn’t adjustable at all.
I have found one that I think will work, but I’d like some guidance. One thing that confuses me is the brass ******* that thread into the manifold. Do I need those, or can I just thread quick connects directly into the manifold.
This isn’t going to get heavy or professional use, so I don’t want to spend a lot of money.
Manifold on Amazon
Pictures below of the current set up.

 

[Citation]

What's wrong with the unloader? Does it constantly leak or never unload.

By non-adjustable do you mean no pressure regulator?

I'm not sure total replacement is the best plan but I'm also not 100% on the real problem.

 

[MikeH]

I think the unloader is bad because it doesn’t usually kick back on when the pressure gets low. You have to drain the tank entirely before it will come on. Occasionally, if you’re using air fast enough when it should come on, it will, but not normally.
and yes, there is no pressure regulator. You’re always using full tank pressure.

 

[NakeDiesel]

I don't believe your issue is the unloader valve. I just finished fixing/replacing my unloader valve on my eaton compressor. All an unloader valve does is release pressure on the compressor heads after it stops running so that it's easier to start next time.

This is the unloader valve on mine. Inside that brass 90 is a Schrader valve that a rod presses in on it to open it when the compressor stops running.


I'm betting it's an issue with your switch box

 

[MikeH]

that’s possible. Like I say, I’ve never tried to fix one of these before. I feel like I could hear it trying to do something ( it got demoted, so it’s been a year or so since I used it and my memory is fuzzy). Because of that, I didn’t think it was the switch. I did enough research to find the unloader possibility and stopped there.
if it is the switch box, will it be cheaper to replace the switch box, and also add a regulator than to just replace the whole thing? It isn’t like the parts there are super high end or anything, just cheap Chinese like what I’d replace it with. I’m open to advice though.

 

[NakeDiesel]

I'd replace the switch box. You can add a regulator on to it, just remove the quick connect and plumb one between the switch box and quick connect.

My setup is a little more complex as I have an Eaton 2 stage 80 gallon vertical compressor.

 

[Citation]

Currently I don't think you really know what is wrong with the thing. My guess is it isn't the unloader and it could be a bad starter or run capacitor. If it really is the unloader then you won't hear it vent when the pump shuts off. It should start just fine if you wait long enough for the pressure to bleed off naturally (say a few hours).

Does your compressor hold air for at least a few days when not used? It will make things easier to figure out if we at least know that.

Here is how you can check. Run it until it shuts off. Look at where the pressure switch actually pushes on the unloader valve. Did it move the valve? Did you hear the air rush out when the pump turned off? If yes, then your unloader valve is good. A second way to check is fill the thing up then leave it alone for a few hours. During that time the pressure in the line from the pump to the check valve going into the tank should bleed off. See if it will start (you may have to bleed out some tank pressure to get it low enough).


Looking at the pressure switch...
Do you know if the pressure switch actually turns on/off when it should? I'm guessing that is something like a 120psi max compressor. Fill it up then unplug it when the motor turns off. Leave the switch on. Now when the pressure bleeds down to the lower pressure limit (probably 100 psi) you should hear the switch click. You should also feel that when the pressure is high (above the lower limit) the switch doesn't have much resistance. When the pressure is low the difference between on and off will be bigger. If you bleed the tank pressure down and you don't hear/feel the switch click to turn the motor on then you may have a bad switch. If you do feel it but the click over pressure is say 60 psi then you know the switch is out of adjustment/bad, Note these switches generally can be adjusted so you may just need to set the cut in/cut out pressure correctly.

If you have a bad run capacitor the motor will struggle to build full pressure. It doesn't sound like that is your issue. If you have a bad starter capacitor then you may have issues starting because the motor isn't getting up to speed before the pressure in the head is too much to handle at low RPM.

Do you know if the pump is running at it's rated speed? Time how long it takes to go from empty to full. For example this one:

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This calculator says an 8 gallon compressor filled with a 4 cfm pump will take about 2:11 (min:sec) to go from empty to 120psi. If your compressor takes a lot longer than the estimate then it could be a motor or pump issue.

 

[MikeH]

Thanks for all those troubleshooting steps. I’ll answer as many of the questions as I can and start investigating the rest.
first of all, yes, it does hold pressure for several days without losing it. The guy I bought it from said that he had been having trouble with it leaking, so he pulled it all apart and rewrapped everything. He must have done a good job because Ethan has never been an issue.
I don’t remember if there’s a rush of air when the pump turns off, but will check that.
mad for kicking back on, if I’m using a tool that uses a lot of air, and am continuously using it as it approaches the lower limit (probably 100, but I don’t know), it will come on. If I’m using it intermittently, or if something like my super leaky ratchet is on it, it gets down to 100 slowly and doesn’t come on. At that point, I haven’t been able to get it to come back on without draining the whole tank to zero. Then it cheerfully kicks on again. I’ll try some of your steps and see how they go.
I want it to work right though, because it is now extra and I want to pass it on to a friend.

 

[dave*99]

OP, The unloader and the switch are part of the same component on your compressor. The small horizontal brass finger sticking out of the switch box presses on the Schrader valve in the vertical brass fitting on the right side of the switch. That is the unloader. The brass finger of part of the switch mechanism. Replacing the switch (black box) should fix your problem.

Lubricating the switch internals may help too. You say it switched a little better if you draw air fast, and fails if you draw air slow. That's a sticking switch. Fast draw snaps the switch better - slow draw allows it to stick.

Just my $.02

 

[MikeH]

OP, The unloader and the switch are part of the same component on your compressor. The small horizontal brass finger sticking out of the switch box presses on the Schrader valve in the vertical brass fitting on the right side of the switch. That is the unloader. The brass finger of part of the switch mechanism. Replacing the switch (black box) should fix your problem.

Lubricating the switch internals may help too. You say it switched a little better if you draw air fast, and fails if you draw air slow. That's a sticking switch. Fast draw snaps the switch better - slow draw allows it to stick.

Just my $.02

Silicone spray? Or what else should I use to lubricate it?

if I end up just replacing the switch box, I’ll have to either find some sort of part number or failing that, know how to match what I need. I don’t assume they’re standardized, are they?

 

[The Cobbler]

sounds to me like your pressure switch is bad. but, you need to properly diagnose before you throw parts at it.
if it was mine, doing that , I would run the pressure up, bleed it off to below where it should kick on, umplug it, jump the pressure switch wires, and then plug it back in. I am pretty sure it will start . do that a few times to be sure your findings aren't a fluke

 

[dave*99]

Take the black cover off the switch box. Stare at it while you bleed the air off fast and again while slow. Confirm it is acting improperly. Look at how it works. A drop of light oil on the appropriate mechanical points will help. It should be obvious where the friction points are. Silicone spray may work, but may not last as long. It's worth a try.

 

[Citation]

A gummed up pressure switch certainly could be the cause here. Worth opening it up and taking a look. Be careful about using any lubricants since the switch can throw sparks when the motor shuts off.

A new pressure switch assembly may be the answer here.

 

[The Cobbler]

... just because the contacts are closing, doesn't mean they are making contact . the points could burned. an ohm test on the closed points (without being powered up) could tell a story too

 

[seber]

Pressure switch without a doubt. It is a simple unit and they are universal. Disconnect the power, take the cover off and move the contact lever. That is what turns it on and off. Once you have done that, you will have a better idea of how it works. It is possible that it simply lost it's adjustment. Directions are inside the cover. The red lever on the side is a disconnect. It will move the contacts out of engagement.

 

[redmondjp]

Amazon has the Square D pressure controllers, and their are dozens of flavors of them, with options ranging from unloader yes/no (yours is yes), switch built in (yours has a switch), pressure control range values, and also if adjustable or not, horsepower rating (there is a lighter-duty and heavier-duty version), and number/size of air ports. They are $30-60, or used to be the last time that I checked. I would not buy a Chinesium one ("LeFoo" or other such brand) personally, just to save a few bucks. With a bit of research, you should be able to find a direct replacement for yours, if needed.

I'm in agreement with the above that it sounds like your pressure switch is sticky. There is a diaphragm with compressed air on one side that moves the diaphragm which is connected to the switch contacts. You may be able to un-gunk yours to fix it. It's a pretty simple device once you understand how it works. Don't be afraid to take it apart - you don't really have a lot to lose at this point.