Question about Dewalt D55168 1.8 HP Wheeled Portable Electric Workshop Compressor

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Dewalt D55168 air compressor runs until 95 psi and never stops. Pressure never goes above 95 psi. It use to stop around 140 psi.

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  • eclipsem66 Apr 01, 2011

    There were no leaks anywhere, i checked the Rubber O rings in front and behind the valve plate and there was no damage at all. When the machine is off nothing is leaking.



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If you have no leaks the first thing I'd check is the ring and cylinder for wear. The cylinder wear is usually pretty obvious, but if you can see light around the piston ring it's bad. The replacement part number is N038785. Also check to make sure no valves on the valve plate part number A09819 are broken or bent.

Posted on Dec 16, 2011

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Check for leaks all over the machine. Possibly the O ring on the drain valve is damaged. If the machine is oil-less, the big rubber O ring on the piston could be worn away.
When the machine is turned off can you hear air leaking from anywhere?

Posted on Mar 31, 2011

  • eclipsem66 Apr 01, 2011

    I check all over, and there were no leaks. Drain valve works properly, but does have a little water coming out of it when i purge it. I check both rubber O rings in front and behind the valve plate, no damage. When the machine is off, i dont hear anything leaking.

  • EugenesDIYDen
    EugenesDIYDen Apr 04, 2011

    Here is the parts schematic for the compressor:

    The piston ring may be damaged or worn or there may be a broken reed on the valve plate.



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Makita MAC5200.Brand new.Just broke-in. Pressure goes to 140 PSI and stops.Tries restart at 110 PSI.Motor"Humms"only.Will not restart until pressure below 20PSI.
There is a part called an unloader. It reduces the pressure on the compressor when the unit stops at the desired pressure. The actual unloader may be part of number 50 in this diagram.

Dec 18, 2016 | Makita Air Tools & Compressors

1 Answer


If you bought it at HD return it for a new one. If not you will need to use a meter and check power from receptacle to on/off switch to pressure switch., Check motor winding. If all else fails call Dewalt and they will help you.dfffd6xqamff+a17gofmrmxewaaaaaelftksuqmccaa==

Nov 30, 2017 | Dewalt D55168 1.8 HP Wheeled Portable...

1 Answer

I have a D55168 Dewalt compressor. Since I've had it, it has never shut off automatically and I've always shut it off manually at 200 psi. If I leave it alone, will it automatically shut itself...

Your concern is very well placed, at pressures that high a lot of damage can be caused by a failure. According to the manual for this model air compressor the approximate cut-in pressure is 160 psi and the approximate cut-out pressure is 200 psi. Meaning it should pump up to 'about' 200 psi and shut off and not come on again until it gets down to 'about' 160 psi. They say approximate and I say about because it's not an exact science setting the pressure switch. Spring rates are not always exact, pressure guages are not that precise, etc. When turned on, it should shut off at 200 psi +/- 10 lbs. If it goes more than 10 lbs over that (220psi), I'd recommend you get the pressure switch and or guages checked or replaced.

Jun 16, 2011 | Dewalt D55168 1.8 HP Wheeled Portable...

1 Answer

Dewalt air compressor keeps running until pressure output is 200 PSI, the same pressure in the tank. Why doesn't it quit running at 120 PSI the designated pressure on the compressor?

The regulator switch/unloader is bad or out of adjustment. Perhaps though the gauge is faulty. 200 psi in a 120psi compressor is dangerous, don't run it until it is fixed!

Dec 15, 2010 | Dewalt Air Tools & Compressors

1 Answer

I have a dewalt D55168 air compresser. motor stays running ,air pressure won't go over 35 psi.. thanks , frank n2141s

Here is a parts diagram for the air compressor:


There are a couple of things to look for on the air compressor.

You will need to see if the piston ring is damaged or if you have a broken reed on the valve plate.


These are typically the two most common problems with this model.


Oct 12, 2010 | Dewalt Air Tools & Compressors

1 Answer

Motor "bogs down" at roughly 120 psi...almost stops

You suspect this unit as being a two stage because of the unusually high cut off pressure. It is a single stage and the motor really has a difficult task and is being pushed to the limits. to reach this pressure. We usually reset the pressure to lower setting ~~ say around 140. Your pump probably has a leaking intank check valve (brass fitting at tank) or leaking valve plate in pump. Simple tests : with pressure in tank unplug compressor from outlet and listens for air leak around pressure switch. As you unplug the running compressor from outlet you should hear air leaking from pressure switch for just a moment as air is let out of airline from pump to tank. If air leaks out till zero pressure then change the valve. If tank holds pressure then valve probably ok. Next test, with no air in tank and air filter removed, plug in compressor and feel intake port for strong suction. If the valve plate is bad, suction will decrease as pressure neers the 120 mark till the point of feeling that air is actually blowing out of intake. With good valve plate there will be strong suction untill unit reaches set pressure. If valve plate is bad also change the cylinder and piston ring. Good luck with your repair.

Jul 28, 2010 | Dewalt 2 Hp 4 GAL Air Compressor

1 Answer

Compressor blows off, does not maintain pressure

Hi there. This is normal. The pressure is set to stop at around 120-140 PSI as a safety measure. It probably kicks in again around 80 PSI so as to remain pressurized between 80 and 140 PSI. Since most air tools operate in this range, it is ok for the compressor to maintain pressure in that range. You do not want to adjust the maximum pressure safety release valve as it could be extremely dangerous as certain components in the compressor may only be rated up to 140 PSI or slightly higher before they fail or blow apart.

Jul 25, 2009 | Porter Cable 18 - Gauge Brad Nailer and...

1 Answer

D55168 lost compression while running

The dewalt model d55168 is a high-end oil-free compressor. Oil free compressors could have a short life span due to dusty or dirty conditions at the job site. The cylinder of your compressor is open from the bottom and will **** in debris scratching the cylinder/ silicone-vinyl piston ring reducing pressure. However the reduction in pressure will be over time till the point that the compressor will not reach cut-out pressure and just keep running. If you lost pressure suddenly to "0" then you probably lost the drive belt. A replacement can be found at a local dewalt service center or ordered thru When you take down the compressor, be sure to examine the cylinder /piston for wear. These are the two most common problems. Good Luck on your repair and email if you have other questions.

Mar 25, 2009 | Dewalt 2 Hp 4 GAL Air Compressor

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