unloader valve on lefoo lf10-4h pressure switch

by Kent

lefoo lf10-4h pressure switch. I know you said why would anybody want to set their unloader valve. Well I need to mine because I turned the screw thinking I had the right adjustment well I did not. Now as compressor builds pressure motor strains then pops circuit. Cut in I believe is 85 cut out like 115 but so many screws have been turned I do not know anymore left from right up from down. Thanks KJR

Hello Kent... well, I have to admit, I'm a bit puzzled by your question/comment.

I read that you've been adjusting the cut in and cut out of your pressure switch settings by turning screws in the pressure switch... OK, I get that.

I'm not quite sure how "why would anybody want to set their unloader valve." fits with your pressure switch issue?

And, I'm wondering what makes you think that it's the cut in and cut out that's making your compressor motor strain and pop breakers.

Perhaps you would comment here with some specifics?

For instance, what is the pressure on the tank gauge when your compressor motor starts to strain? Empty the tank, close the tank drain, start the compressor, and note this pressure please.

What is the make and model of your air compressor?

How is it being powered? By that, I mean, do you plug it into a wall socket, or are you using a power bar or extension cord?

Lets start with these.



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May 04, 2013
Unloader Issue
by: Kent

Bill the compressor from empty starts fine but as it reaches the cut off point motor bogs then throws breaker. The first few times it worked correctly .It was not until I decided to mess with what I know now to be the unloader valve that this issue of throwing the breaker arose.I have yet to decide what my next step is. All local supply places do not carry the correct pressure switch.I will just keep plodding forward and see what what arise.Thanks for your help thus far.
If the compressor starts fine with an empty tank, but won't start with pressure in the tank, that suggests that the unloader valve is not opening when the tank pressure reaches cut out.

"but as it reaches the cut off point motor bogs then throws breaker." but this suggests that the problem is not the unloader or the pressure switch. If a motor bogs down as the pressure builds, then it could be a run capacitor, could be the intake valve or more likely the high pressure valve inside the pump, it could be that the intake filter is plugged up, the tank check valve is not working properly, many things.

But not the pressure switch.


May 03, 2013
Unloader Info.
by: kent

Menards House brand plugs to socket Adjusted unloader valve first then stopped operating correctly . Cut is around 80-85 and cut out is 100-110 worked until I thought settings were wrong.turned unloader screw first hasnt worked right since. Starts to build pressure motor starts to bog then throws breaker,When fisrt starting sounds normal,
OK, unloader valve and pressure switch two different items... got it!

If you drain the tank to zero PSI, and then start the compressor does it start OK and then pressurize up to normal cut out?

If so, make sure that your unloader valve actually unloads when the compressor stops. If it does not, air trapped over the piston will lead to your compressor symptoms on start up when you have pressure in the tank.

I have never adjusted an unloader valve. My workshop compressor has an exterior unloader, and if it were adjustable, I suspect all I could is move the height of it to ensure that the toggle from the pressure switch pushes and releases the valve pin as the compressor cycles.

See the unloader valve page for more info.


May 03, 2013
Unloader Issue
by: Kent

Bill the unloader staement/issue arose from the fact that was the first screw adjusted. Now to back up and supply details as I should of from the start. Compressor is a menards house brand I believe. I assume this because an internet search of service number comes back to them. The compressor pumped air and shut off just fine at approx. 100 psi and cut in at 80 pis I thought that was inncorrect cut out pressure so I set out to adjust hence my issue at hand. After some reading I have learned that adjusting the unloader is not wise and that by being out of adjustment can cause the compressor when under load to trip the house breaker (no power strip/direct plug)I understand this is because of pressure being built up and not being properly released(at least I think this right). So in a nut shell that is where I am at

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air compressor cycles on and off rapidly

When I plugged my air compressor into the 120 vac outlet, the motor starting cycling on and off in a rapid fashion. I cannot tell if it is the pressure switch or one of the capacitors.

Bill says...

Are you comfortable with bypassing the pressure switch, only long enough to see if the compressor runs normally? That's what I would do, to see if that would isolate the pressure switch as the problem.

Know that your air compressor will not shut off if you bypass the switch to see if the compressor will run normally, so be careful.

And if you aren't comfortable mucking about with electricity, take the compressor to a shop and ask them to.

Bypassing the switch will tell you right away if the switch is the problem if the compressor starts and runs normally with the pressure switch out of the circuit.



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Jun 24, 2014
brush wire
by: Mark

I bypassed the regulator and my compressor had the one same problem, then I took the motor out and found that one of the brushes had only a strand of wire that electricity was running through. hope this helps
Mark, I expect it will. Thanks for providing this info.


Oct 05, 2011
by: Terry

Thanks. That is a good idea. I am comfortable doing that so I will try that this weekend.


Good stuff, Terry. Maybe you could comment here on how it turned out?



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Pressure switch for Webster air compressor

Hi Bill, I just purchased an old Webster brand twin cylinder air compressor with a 20 gallon tank.

It has a gauge at one end of the tank to tell you what pressure is in the tank and a couple of relief valve type things on the other end.

Basically when the compressor is running it keeps compressing until about 125psi then the relief valve kicks in and vents any excessive pressure and the motor keeps running to compress more air.

Also there is no on/off switch, the only way to shut it off is to unplug from the wall.

It runs on 110V.

I would like to add a pressure regulator and a pressure cut off switch rather than have all my compressed air vented.

I've seen a combined pressure regulator/cut off switch on an old Speedaire compressor online so know they exist.

Do you have any leads on where I might find one? I have a CH nail gun I'd like to run at 90psi but have no way of regulating the compressor to that.


Richard, I don't know the compressor and have not been able to find any information on the old Webster air compressor you have.

Having said that, I can see no reason why you cannot simply run the power supply to the motor circuit through a standard pressure switch to toggle the motor on and off at the pressure switch set points.

A twin cylinder compressor will typically have a PRV in the line between the cylinders, to prevent catastrophic pressure buildup in the line should the inlet valve on the second cylinder fail closed.

I don't know about the two PRV's on the other end of the tank.

I hope someone knows the original operating ranges of this compressor to give you some idea of what the safe range is.

If the PRV's are popping off at 120 PSI, and they are not failing, then that would suggest that 120 PSI is already well into the danger zone for the compressor.

As to regulating the pressure to 90 PSI to the air tool, see the regulator page or ebook for details on what they are and what they do. A regulator is what you need for air pressure control to your air tools.


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My PC compressor flips the breaker at 120 psi

by Chase
(Bothell, Wa. USA)

First, thanks for taking the time and making the effort to help all of us newbies out here.

Now, I have a PC 135 psi 6hp 25 gal upright compressor. It will run up to 120 psi and then shut off. When it shuts off, it blows the 20 amp breaker. Doesn't matter what circuit its on, I've tried 3 or 4 different circuits and it blows them all.

Of course this doesn't happen 100% of the time. Just 99.999% of the time. In other words, it has operated properly 2 or 3 times over the lifetime of my ownership (I bought it used), and I have used it often in the last 5 years or so.

From what I have read it sounds like the pressure switch is shorting, and perhaps needs to be cleaned or replaced. Can you tell me if this is true, and if so, how I go about taking it apart, cleaning, and reassembling?



Bill says...

Chase, yup, it could be the pressure switch, but that might be too easy.

I think you do have a short to ground when the compressor stops, and it could be the switch, but it might also be a capacitor or the motor windings themselves.

Run it again though, this time with the cover of the switch off so you can see if it arcs a whole bunch when it reaches cut out pressure.

Or, see the check the capacitor page, and start there. If they check out OK, then the least expensive next step is to change the pressure switch. I doubt that it is possible to find replacement parts for them.

You can use some compressed air to blow the switch out if you want to try that.

Be careful with the power. 240 Volts to ground through you is a sure, quick, death!



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Apr 02, 2016
Hooking up compressor unloader valve
by: Bill

Butch, this switch has the unloader valve on the side I believe, and yes, you do need to connect the line over from the tank check valve fitting.

See the pages on this site about unloader valves and tank check valves to better understand what these compressor components do, and why they are important.

Apr 02, 2016
LF 10-4H
by: Butch

Does anyone know on these models do you have to hook up the unloader valve or will it operate normal with it un-hooked

Jan 05, 2012
by: Anonymous

Amen brother. My grandfather almost died when he drilled through a 110v line and couldn't disconnect from it (he was under a house and squished into the space). And that was just 110v.

I have seen the results of 440v through one arm and out the left leg. Ugly with a capital "UG".

Thanks for the info, will try it at first opportunity.


10-4. Good luck.

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