DeWalt D55140 Air Compressor Won't Shut Off.


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Old 09-13-22, 02:22 PM
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DeWalt D55140 Air Compressor Won't Shut Off.

DeWalt D55140 Air Compressor Won't Shut Off. After the tank pressure reaches the regulated pressure, it will no longer shut off. Air will escape from the regulator knob as the compressor runs. Does this usually happen if the pressure switch inside the case is faulty? I changed the whole regulator manifold a couple of years ago (as this model does not allow just the knob to be replaced) No other leaks. How do I test the switch? Another $100.00 regulator manifold or an $18.00 switch.
 
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Old 09-13-22, 07:12 PM
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It's just the pressure switch that is bad.
I'm seeing multiple air pressure replacements.
Make sure you are getting the pressure you want or your machine requires.

pressure switch
 
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Old 09-14-22, 06:43 PM
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Sounds like a bad regulator to me. In general on a compressor, the tank should build full pressure and shut off at whatever the factory setting is on the pressure switch, probably 90 psi or so. The regulator doesn't turn off the compressor, it just regulates the pressure at the hose. If it keep s letting air out, the tank will never reach the pressure required to shut it off.
 
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Old 09-14-22, 07:24 PM
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That compressor uses a non adjustable pressure switch to operate the motor.
Most places show it as on at 120psi and off at 150psi.

However.... on a second review.... the pressure should be able to go well over the regulator setting without leaking. That would point to a leaking regulator.
 

Last edited by PJmax; 09-14-22 at 07:48 PM.
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Old 09-15-22, 08:18 AM
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DeWalt D55140 -Type2
I changed out the whole manifold a couple of years ago. As you noted, the regulator is nonadjustable and cannot be replaced or repaired separately from the manifold. The regulator knob is between the tank pressure gauge and the regulated pressure gauge and is a part of the manifold assembly. Picture at the attached link.
Air escapes from this knob once the tank pressure has matched the regulated pressure, but the compressor keeps running. There is a separate pressure release valve on the side. I don't think I shall invest any more money in this. I would have if it was only the pressure switch, but not another manifold.

Manifold Assy. [5140062-33] for Power Tools | eReplacement Parts
 
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Old 09-15-22, 11:41 AM
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The air releases through the knob once it has reached the regulated setting. I can turn the regulator knob as tight as it will go, turn off the compressor at say 100psi and air will not escape through the knob. It only starts to escape once the tank pressure has matched the regulated pressure setting.
 
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Old 09-15-22, 06:39 PM
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Yes.... I understand that. I think that's called regulator unloading.

What do you use it for ?
It's not the end of the compressor.
I have a Campbell/Hausfeld with a defective regulator.
I removed it and connected the air fitting directly. It's rarely you need a regulator.

They offer a basic replacement manifold and you re-use the gauges..... for the type 1 compressor.
I suspect you have the later type 2 compressor which requires the entire assy be replaced.
I'm seeing regulator rebuild kits but not for the D55140.

 
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Old 09-15-22, 07:08 PM
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Right, already replaced the regulator (had to buy the whole manifold as it is the Type 2) for a hundred bucks. A whole new D55140 is only sixty bucks more. I can use it for pin nailing and finish nailing but have to keep turning it on and off by hand.
 
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Old 09-16-22, 03:23 AM
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Would adding an inline regulator make it usable without having to turn it off/on?
https://www.harborfreight.com/brass-...tor-68220.html
 
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Old 09-16-22, 07:45 AM
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At three bucks, not much to lose! Thanks for the suggestion, will give it a try.
 
 

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