Any air compressor experts here?

[john bateman]

I have this Dewalt air compressor.
http://www.dewalt.com/us/products/tool_detail.asp?productID=15014
http://www.dewalt.com//ProductImages/PC_Graphics/PHOTOS/DEWALT/TOOLS/MEDIUM/5/D55168_1.gif

Its about 2 years old, hobbyist use only. The motor runs maybe 1 to 2 hours per month. Normally it charges the tank to 200psi, shuts off, then turns back on when the pressure drops to 150psi.

Recently it seems to be taking longer to pressurize the tank. On 2 occasions, after a couple of on/off cycles, it was unable to reach 200psi. It would get up to about 160psi and just run continuosly, till I shut it off. When I turned it back on after 15 minutes, it worked normally for a few cycles, then exhibited the same problem.

I assume something in the pump is wearing out. Does this seem like something a diy'er could repair?

Here's the service drawing/parts list:
http://www.dewaltservicenet.com/Products/DocumentView.aspx?productid=66646&typeId=15502&documentId=33925

Thanks for any advice.

[Bill Huber]

When the unit is running and it is at say the 160 lb. but is still running and not shutting off, do you hear air leaking out.

If the auto shut off value is sticking or leaking it will do that.

On my old one I had that problem, the value would let air past but would not let the compressor run long enough to get up to the pressure I had it set for. I put a new auto shut off and that fixed mine.

My compressor is just set for 120 lb. I really don't see why you would want it set to 200, that is working the compressor a lot.

[johnny means]

sounds like a leak between the compressor and the tank. This is commonly caused by a vibrating motor attached to a hard air line.

[Marty Paulus]

I was thinking the 200 psi is high for a compressor as well until I hit the link. Dewalt says 200. My guess is the pressure is that high to help with the SCFM rating of the compressor.

One thing to watch for is the oil less compressor. I haven't read a lot of good things with those style compressors. From what I have read they tend to be louder and have a shorter life then an oiled compressor. Think car engine here. You do not see any gasoline engines that run without oil and all an engine is, when you build them anyway, is a big air pump. I know some of the smaller 12V units say not to run them more then a few minutes at a time without letting them cool down. But then again they do not put oil into the compressed air. Have to balance something I guess...

[john bateman]

Bill,The reason it charges to 200psi is because it was designed that way...it fits more air into the tank. I can't hear a leak when it's running. It's an oiless and pretty loud.

Johnny, Wouldn't the air leak out if that was the case?
The tank will stay pressurized for days when there is no tool attached to it.

[David Christopher]

John, the problem is the reed valves..they wear after a while of use. you wont hear the leaking its just the valves not seating

[Bill Davis]

I second Dave's view of the likely problem. Since something has changed from previous operation, and since the reed valves are thin and are worked a lot as the compressor is pumping, they could be the cause.

My first compressor was bought used from a contractor who used it for painting, i.e. relatively higher usage cycles than the average home shop. It would pump pressure but had a very hard time getting that final amount of pressure to allow it to shut off. The price was right and I bought it. Rebuilt the head assembly where the reed valves are located (just general cleaning and replacing of the reeds). Ran for years after that working beautifully without long run times and failure to reach cutoff pressure.

It's well worth looking into.

[john bateman]

So are you two referring to the valve assy, part #85 in the drawing? To replace it and the O-rings on either side would only be about $25 in parts.

If I'm going to the trouble of tearing it apart, I'd just as soon have the replacement parts in advance. (sorry for the oversize image)
http://www.dewaltservicenet.com/documents/English/Exploded%20Art/EA023089.gif

[David Christopher]

So are you two referring to the valve assy, part #85 in the drawing? To replace it and the O-rings on either side would only be about $25 in parts.

If I'm going to the trouble of tearing it apart, I'd just as soon have the replacement parts in advance. (sorry for the oversize image)
http://www.dewaltservicenet.com/documents/English/Exploded%20Art/EA023089.gif

yes..................

[Ken Fitzgerald]

That Dave guy responded like he's a Machinist Mate.:confused:

[David Christopher]

That Dave guy responded like he's a Machinist Mate.:confused:

Ken, thats allmost an insult...LOL,,,ENGINEMAN for life

[Ken Fitzgerald]

Ooooooooooooooops!:rolleyes:

[David Christopher]

Ooooooooooooooops!:rolleyes:

No problem Ken, in a few months Ill be a civilian

[Ken Fitzgerald]

No problem Ken, in a few months Ill be a civilian


He said with a smile!:D

Well deserved Dave! Well deserved!

[johnny means]

Bill,The reason it charges to 200psi is because it was designed that way...it fits more air into the tank. I can't hear a leak when it's running. It's an oiless and pretty loud.

Johnny, Wouldn't the air leak out if that was the case?
The tank will stay pressurized for days when there is no tool attached to it.

No, air tanks have check valves to prevent back flow to the compressor. If you had a leaky air line going to the tank (most likely a loose fitting), the only air you would lose would be what fit in the line. I have seen cases where a loose fitting will effectively become a valve, working up to a certain pressure, then leaking out anything above that.