Need help with Maximum Whisper-Tech compressor leak

[eljay]

I have this compressor:

General PDP Template

www.canadiantire.ca

And it leaks air. The leak starts as soon as it is turned on and the tank only pressurizes to 30 psi while it's leaking. It leaks from the exhaust at the pressure switch. When I shut it off, it stops leaking air immediately.
I have cleaned the check valve on the tank, but it leaked the same way. I then ordered a new check valve. However, that one had wrong thread size, so I just ended up using the spring and the plastic puck and put that into my existing cleaned check valve. Same leak and behavior.

So, I'm guessing it's the unloader valve on the pressure switch.
The switch is Lefoo LF10-L4H.
Can this be disassembled and cleaned? Or should I buy a new pressure switch and replace the whole thing?
Is there an alternative switch that will fit and is better made?

Thank you!

 

[The Cobbler]

leefo aren't the best switches , but they are very common on compressors and most seem to hold up not too badly . I replaced one and it lasted a week so I got a bad one.
first thing to look at is the end of the unloader valve . there's a pin that sticks out of the end of the tube that gets depressed when the switch shuts off. that's what allows the air to unload. if it's depressed all the time it can't seal . if there is an air gap when the unit is running look for a bent pin, debris or something else causing the leak . they're not really that complicated once you know how they work
some pictures of the valve showing the unloader port might help too . also make sure the pipe is tight on the fitting, could be as simple as that!

 

[eljay]

Thank you very much!
I will poke around and see if I can clear any debris without removing the whole switch.

I'm quiet sure I killed it with not draining the tank frequently and letting rust sediment migrate to the valve.

 

[scooby074]

Sounds like a leaky unloader. Take it back to crappy tire and exchange it? A quality pressure switch/unloader is 1/3 the cost of that compressor. Plus that assumes that CT used standard pipe thread fittings and not metric ****. It could be a can of worms

 

[eljay]

Unfortunately, it's well past the return option and warranty.

I see some switch options, but they are pricey in Canucklandia.

 

[The Cobbler]

I've owned & repaired a lot of smaller compressors. none have had an oddball switch on them. never seen any without 1/4"NPT .

most unloader valves will separate from the switches . as i said, just don't jump to conclusions before you check for leaks etc on close by fittings

 

[eljay]

Today, I disconnected the copper line at the unloader valve while leaving the other end connected to the check valve.
As soon as I turn on the compressor, air is dumped out of the copper line. When I plug the end eith my finger, the tank starts building pressure easily.
So, it sounds like the check valve on the tank is the problem afterall, correct?
Or does an unloader valve play any role in check valve operation by homding some pressure in the exhaust line?
I believe it only releases any pressure in that line after shutoff so there's no back pressure on the compressor cylinders, correct?

I've tried also putting back my old spring with a new rubber puck into the check valve, but got the same behaviour.
So, I don't know where I can get proper parts to ensure the check valve is sound.

 

[whateg01]

If I understand what you did, then no, your didn't isolate the problem to the check valve. When you disconnected the unloader valve you gave the pump another place to send air to do it doesn't fill the tank.

 

[eljay]

If I understand what you did, then no, your didn't isolate the problem to the check valve. When you disconnected the unloader valve you gave the pump another place to send air to do it doesn't fill the tank.

OK, I see.
So, I should attempt to clean, lubricatw the unloader valve, reconnect the copper line and try again?
This is what the inside of that unloader inlet looks like (bottom of the mirror). Is that OK, or should that needle be poking up and through a bit more?

 

[micromind]

The check valve can be tested by disconnecting it from then pressure switch, holding your thumb on the end, start the compressor let it build pressure for a bit, stop the compressor and release your thumb. You should get a small amount of air out of the tube. If the tube continues to bleed air, and the tank pressure goes down, the check valve is bad.

The small valve on the pressure switch is supposed to close when the compressor is running and open when it stops thus relieving the pressure from the check valve to the compressor discharge.

This is because the compressor will start easier if there's no pressure in the line.

 

[The Cobbler]

as said, the unloader stops air from escaping when the pressure is building, when the pressure switch is satisfied and the compressor shuts down, the unloader opens and lets the air bleed off from the check valve to the compressor so it's now at atmospheric pressure , allowing it to start with no load on it.
it sounds like you have diagnosed a bad unloader valve . I would still like to see a picture of the unloader valve at the pressure switch .particularily where the pin is at the tang on the switch to open it up .

 

[eljay]

Thank you!
That is exactly what is happening: I can plug the end of the copper tube and the tank builds pressure easily and I stop it and release the hold on the tube, there's only that tiny puff of air, but the tank easily holds pressure with no leaks.
So yes, it is the unloader valve.

Is the inlet to that valve supposed to look like this?
The orifice looks very irregular and the pin does not seems centered there.

 

[eljay]

And here are more pics of the pressure switch. It's hard to get a picture of the valve parts.
Is it possible to service that valve or should I just buy a whole new switch?
And should I go for the same model or is there and better option that fits these compressors with correct ports and threads?

 

[The Cobbler]

can't really tell for sure, but it looks like there's some rusting inside there. which would make sense why it's leaking .
is that the tube side with the tube removed or is the tube on the other side?

 

[eljay]

can;t really tell for sure, but it looks like there's some rusting inside there. which would make sense why it's leaking .
is that the tube side with the tube removed or is thee tube on the other side?

That's the tube side with tube removed, so it's the unloader valve inlet coming from the check valve.

 

[The Cobbler]

ok, so the other side, there's a pin that comes out of the housing... is there air space between it & the tab on the switch? or does the pin touch the tab?

 

[eljay]

In this circled area? There's space there

 

[The Cobbler]

show me the other side of the picture in post #12

 

[whateg01]

I don't suppose you did the soapy water thing before to see where the air is actually leaking. That fitting a few posts back looks a little buggered to me.

 

[eljay]

show me the other side of the picture in post #12

That is the area circled in the picture in post #17.
There is no pin in that circled area.
I can push the "plunger" From the inlet side (the middle of picture in #12) and I can see a pin come up into the space circled in #17.

 

[eljay]

I don't suppose you did the soapy water thing before to see where the air is actually leaking. That fitting a few posts back looks a little buggered to me.

I didn't. Do you mean the check valve or the unloader valve inlet fitting?

I don't think I have a fitting leak since the unloader valve begins dumping air as soon as I turn on the compressor and the tank builds pressure up to 30 psi and will not go any higher and just sit there running while the air is escaping through the unloader valve exhaust. If feels like the spring or plunger gets stuck in a position that maintains ~30 psi.

 

[The Cobbler]

it's probably the CFM of the compressor can maintain 30psi with the leak, that's why it won't go higher.
sorry & can't visualize what you;re saying in 20

 

[eljay]

I managed to find a pic of what the inketvof the unloader valve should look like. It's clear that my valve fitting as pictured in post #12, is corroded around the center.
So, the question is whether that valve can be replaced separately or do I need a whole new switch?
I found here for US$42 with shipping to Canada: https://www.opentip.com/Interstate-...its-Dewalt-Hitachi-Emglo-Port-p-12683621.html

 

[The Cobbler]

let me look in my scrap parts pile & see what I've got. I know I have a few switches like that . not sure about the unloader valves .
if I have one, pay for shipping & you can have it

 

[eljay]

Oh, that's kind of you. Thank you.

I saw their other 4-port model that has the unloader valve mounted the side, so it should be easily serviceable or replaceable:
Lefoo Quality Air Compressor Pressure Switch Control 95-125 PSI 4 Port w/Unloader LF10-4H-1-NPT1/4-95-125 https://www.amazon.ca/dp/B00QHZPUKC/?tag=atomicindus04-20

But to use, I'd have to get a new copper tubing and bend it around the front to feed that unloader valve since it's facing forward while mine is at the back of the switch. I may just do that if this switch is compatible.
BTW, is it necessary to use copper.tubing for the exhaust line? Can't I just use normal air hose? I feel like I'm damaging the copper connection each time I fiddle with it.

 

[eljay]

I picked up a cheap 4-port switch on Amazon and swapped and my compressor is alive again!
Thank you everyone for your help!
Here are the pictures of the unloader valve on the original Lefoo switch. I hoped to keep the 'metal' part on the tank, but the unloader valve on the new switch is spaced a bit differently, so I didn't want to risk it not working and swapped the whole thing.
The switch only cost $15 on Amazon and feels and looks like from Toys R Us, so I don't expect it will last long. I will see if I can find the same unloader valve and refurbish my original switch and have it ready.
After re-assembly, everything worked fine, but I'm losing about 10psi over 24 hours, which doesn't bother me for my uses. I'm guessing my connection to the tank is the culprit as I only turned it hand-tight as it's impossible to get any kind of tool on it to turn it. I used teflon tapeon all connections.

Thanks again everyone.

 

[The Cobbler]

great. I looked and forgot to get back to you. I don't have one.
as far as the leak, I've had pressure switches leak between the housing & the aluminum port connections. a tighten of the 4 screws that hold it together was all it took . some soapy water sprayed on all your connections will find the leak

 

[eljay]

great. I looked and forgot to get back to you. I don't have one.
as far as the leak, I've had pressure switches leak between the housing & the aluminum port connections. a tighten of the 4 screws that hold it together was all it took . some soapy water sprayed on all your connections will find the leak

Thank you! I will check that. This cheap one is using tiny nuts instead of a plate with predrilled slots and it was very annoying trying to get them on.

After all this, I still trying to understand how this unloader valve hold pressure during operation, but opens right after. That little pin inside it has extremely little resistance, so I'm puzzled how it operates againts the tank pressure.

 

[northturk]

I also have a Maximum Whisper-Tech compressor- 10 Gallon. It is less than a year old and worked fine until today. Even with the pressure regulator turned off and no tools attached, It pressures up to about 85psi in the tank and stays there. But the motor keeps running until I shut it off.
And when I do, the tank gauge stays at 85, and I can’t find a leak and it doesn’t seem there is one. So basically, everything is working, but the motor won’t shut itself off. Any suggestions?

 

[The Cobbler]

pressures up to about 85psi in the tank and stays there

check that the gauge is not defective.
bad or worn ring , valve plate or a leak in the plumbing between the compressor head and tank check valve