Air Compressor Help!

[inane2]

Good evening guys,

My vintage 14 gallon Sanborn pump laid down on my this weekend (I'll save that for another thread!) I have a new 60 gallon compressor waiting on me in the corner but I'm in the process of a remodel and haven't gotten to the electric yet as I have no 220.

Picked up a 25 gallon Craftsman Professional over the weekend, sweet CL find. It was bought new in 2010 and has lived a simple life in small garage airing up tires, etc.

The owner was selling it because he said it would often trip his breaker. We started it up, built up to 175 and kicked out. We ran it down to 145 and when it tried to kick back in, the motor locked and hummed. He then showed me he turned the switch off, ran the pressure all the way down, turned the switch back on and the compressor fired up and ran back up to 175 with no problems. I quickly bought it up and headed home.

Once back at the shop, I found that the lowest PSI that it will fire back up is 20 psi.

The compressor uses a common D26613 pressure switch but it costs more than what I give for the compressor.

With it's cover off:

I'm thinking the problem is in the unloader valve itself. It really seems like there's still air on top of the piston when it tries to restart.

After travelling to the end of the internet, I found the valve by itself on eBay:

Craftsman 69D109740 Furnas Hubble Pressure Switch Unloader Valve DeVilbiss | eBay

Do you all think this is the problem? Anyone know of any other compressor parts suppliers?

Thanks!

 

[puckgrinder85]

Its one of the more common issues, not saying its yours. I know ours hisses as it bleeds the air pressure off after shutdown.

 

[SPYDERLK]

. Yes. You dont want pressure on the piston at start. Its bound to be that unloader valve not functioning and letting tank pressure leak back on the compressor.

 

[skyhook]

When it shut's off, do you hear air bleeding out of the valve, if not,
it's most likely that, let us know if you get er fixed.
It could also be dirty, not sure if these can be cleaned.

 

[Gary Fowler]

The pressure regulator went bad on my Craftsman compressor and Sears wanted over $150 for a new one. I found one at Atwoods for less than $20, installed it over a year ago and it is still working fine. Couldn't believe what Sears wanted for that part. I was ready to buy an new compressor rather than pay the price they wanted for a new regulator.
As for your problem, don't ever run a long extension cord to your compressor, there is too much voltage drop even in a 50' cord to allow the compressor to start. Mine has a 6.5 HP rating (yeah right and runs on a 20 amp breaker)and will not start unless plugged directly into the wall socket OR bleed off the pressure to about 20-30 PSI just as you describe.
Try yours directly to a wall outlet and see if it doesn't work. I suppose it could be the valve, but since I saw all that extension cord, I bet that is your problem

 

[Gary Fowler]

ON another note, do you really need 145-175 PSI service? My compressor only runs to 145 before shutoff and I find that it does well for my uses. I think it cuts on at around 50 which is a little low for impact guns but runs everything else ok. I could adjust the on switch higher if needed just as you could adjust the on pressure down a lot to make it easier to start.

 

[inane2]

Thanks for all the replies guys. Mine doesn't sounds as if it's bleeding anything off when it shuts off at 175 psi. I'm going to loosen the fitting at the unloader valve and see if there is any trapped air there. I'm sure I'll end up removing the valve and checking it over.

Thanks Gary. I do have it plugged directly into the wall. The orange cord in the pic is my air hose. I hear ya' on the 175 psi, I don't need that much. It wouldn't hurt my feelings if it dropped a little lower than 145 and then kicked back on.

Thanks again guys, I'll keep everyone posted.

 

[skyhook]

Good luck, inane2...I wish I could have mine set to 175,,
if you can keep it at that, i would, you can always regulate the output.

 

[PILOON]

Most compressors that I have worked on demonstrating the problem described end up having crud in the unloader valve. Often due to water that blocks the opening and or rust.
The style that has a small cable will have the actual valve at the tank while some valves are directly at the base of the pressure switch.

One way to confirm that the unloader valve is the culprit is to dump all the air using the safety valve* and see if the compressor will then re start without stalling and or tripping a breaker.
Some motors use run and start capacitors which might also be the culprit but from your description I vote for the unloader.

* that is located below the one guage and to the left of the other and has the pull ring installed.

 

[nc redneck]

I would consider start capacitor. Also a hard start kit. Very cheap $ 25.00 bucks or so. Available at any electric motor supply place. Used a lot for older AC units to get a few more years out of them.
Good Luck
Scott

Unloader valve should hiss for about 30 seconds after compressor stops running.

 

[missouri massey man]

I'm thinking if the start capacitor is the culprit, the motor would experience difficulty starting with or without pressure in the tank. First maybe ensure that you DO or DO NOT hear the typical hissing from the unloader immediately at shut down. If no hissing is heard, bleed tank pressure, remove the unloader and clean its internals as good as possible.

Its likely that some rust particulate from inside the tank has lodged within it, creating a blockage. It may be that it will have to be replaced and a less expensive generic replacement that matches your compressors capacity may be difficult to obtain due to the tendacy of Sears to design OEM specific components that make it almost impossible to purchase anywhere other than their own service centers.

 

[missouri massey man]

I forgot to add that the unloader is a two-part device. It primarily is a check valve whose responsibility is to close off and containing the pressre in the tank, then secondarily it allows the pressure contained within the space between the compressor discharge valve and the check valve to be released....thus, the hissing. That short distance in the circuit relieved of pressure allows the compressor to then restart in an "unloaded" condition and not against the tanks "cut-in" pressure.

 

[inane2]

Thanks for all the help guys. Here's an update:

Running the compressor as is, I did not hear a hiss after cut out, unloading the air on top of the piston. I removed the shroud off the motor, built up the pressure and removed the air line that goes into the unloader valve at the pressure switch:





Air rushed out then slowed down but continually came out. However, once I drained the air down to about 145, the compressor kicked in and ran as normal. First time it's done that since I've had it.

I put the air line back in and decided to watch the pressure switch to see if it's actually hitting the unloader valve when it kicks out. Built up pressure, compressor kicked out and a metal plate moved forward to depress the unloader. It acted funny at this part because it still acted like there was pressure and the motor couldn't restart.

Took the screws out of the unloader and removed it from the pressure switch. Hooked it back up the to the air line and decided to experiment.



The needle in the unloader comes out with force when the compressor is running. After it kicks out, I press the needle and bleed the air off. If I hold it in, the compressor will restart. However, if I let it go, the needle pops back out and I can push it back in to unload it once more, but it will pop right back out. So then I removed the check valve in the tank:





Pretty nasty, all rusted up. I put it on the wire wheel, soaked it good with some PB Blaster and put some air (from another source) to it. It opens fine, as it is filling the tank correctly, but it must not be closing all the way creating the leak mentioned earlier. The unloaded valve leaks at its compression fitting if the needle isn't depressed. Once you depress the needle, it resets itself and pops back out.

I'm thinking the unloader is working fine and that the check valve is the ultimate culprit here. Thoughts, suggestions, ideas?

Thanks guys!

 

[missouri massey man]

I do believe you are on top of the problem sir. The rust is typical on compressed air tank internals which is why a manual (or automatic) drain valve should be installed in the bottom of the tank and opened periodically to purge water. Constant exposure to water build up on the bottom of the tank contributes to premature tank failure due to rusting from the inside out.

The automatic drains require a dedicated schedule of periodic maintenance or they will quickly end up like your check valve. The good thing is they can be set up to blow down a few seconds every hour which will go a great distance towards minimizing buildup of water. The bad thing is you don't need that type if your compressor is only used a few times a month. Easier to install a manual valve and force yourself to get on your knees for ten seconds at the end of each work day using the compressor. Kinda wandered off topic a bit.....sorry.

Keep us posted sir. Good luck. Maybe try ereplacementparts.com.... They may or may not have parts for you there, but it is the first place I check for power tool, lawnmower and chainsaw parts among other stuff.

 

[skyhook]

I don't think the check valve is your problem,
however, looking at the check vale, perhaps the line to the "un-loader" valve is full
of junk, see if the line is nice and clean from the unloader back to the tank.

 

[inane2]

Thanks guys. Pulled the unloaded valve line and it is clean. So far, this unit is really clean other than the check valve.

The previous owner replaced the factory draincock with an elbow, a long section of copper and a ball valve on the end. Makes the drain very easy to access.

One thing I forgot to mention, if the tank builds up to 175, it leaks at the unloader valve compression fitting. It will deplete the whole air supply in 4-5 hours.

 

[varmint]

I had a Porter Cable compressor that was very similar- two stage, etc., and it proved to be a great compressor. It should hold air without leaking down... I had to put a small ball valve on my supply line, since the female fitting seemed to leak a tiny bit. I had also put a vall valve and an extension on the bottom to drain it. Once you find the culprit, you'll like this tool, I think.

 

[skyhook]

Thanks guys. Pulled the unloaded valve line and it is clean. So far, this unit is really clean other than the check valve.

The previous owner replaced the factory draincock with an elbow, a long section of copper and a ball valve on the end. Makes the drain very easy to access.

One thing I forgot to mention, if the tank builds up to 175, it leaks at the unloader valve compression fitting. It will deplete the whole air supply in 4-5 hours.

There's your problem, either get a new valve for that pressure or bring down your pressure to 150,
and see how that works.

 

[missouri massey man]

I knew you'd get to the bottom of it !! Thanks for keeping us up to date with the repair sir.

 

[SPYDERLK]

Thanks guys. Pulled the unloaded valve line and it is clean. So far, this unit is really clean other than the check valve.

The previous owner replaced the factory draincock with an elbow, a long section of copper and a ball valve on the end. Makes the drain very easy to access.

One thing I forgot to mention, if the tank builds up to 175, it leaks at the unloader valve compression fitting. It will deplete the whole air supply in 4-5 hours.

That means the check valve is leaking air back into the compressor line. Fix or replace.