Air Compressor Help!

[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.