Help diagnose Craftsman air compressor issue

[Stainless]

My upright Craftsman air compressor (26 gallons) has worked flawlessly for the 9 or so years I've owned it. I went to fire it up today and it's like it won't kick into high gear. It kind of sputters and sometimes won't move at all and just hum. After a few tries, it fired up, but wouldn't do it again after stopping it and trying to restart. See the video:

https://www.youtube.com/watch?v=l7MNhnVXEuI&feature=youtu.be

Anyone have any ideas? I haven't taken anything apart yet as I'm not sure what to look for once it's apart.

[DMC-81]

Hi there,

I have almost exactly the same one. Although I am not an expert, 3 immediate things I would try:

- check that the water has been drained. There should be a drain on the bottom
- check that the air inlet/filter is not plugged up
- after unplugging the unit, take the black cover off the switch box and see if anything is loose.


Good luck.

[Bitsyncmaster]

Most compressors have a way to release the pressure in the "head" of the compressor so it can start the motor before it gets loaded. Not sure how that works but I hear a little hiss when my compressor shuts off. You could verify yours starts by releasing all the tank pressure.

[davidc89]

Is it low on oil?

[content22207_2]

Take the drain plug out of the tank and see if the compressor will run. If it does, the electric motor likely is weak and needs to be rebuilt or replaced.

Bill Robertson
#5939

[Stainless]

You guys are great. Thanks for all the suggestions. I'll see what I can find out by taking the steps outlined.

BTW, it is an oil free compressor, so it's not related to oil being low.

[Citizen]

I have a Craftsman air compressor very similar to this one, based on the picture. It sometimes wouldn't start either, and I think there might not have been enough amperage on the circuit to start the motor and keep it running. Try moving the compressor to another circuit, maybe one without anything else on it, and see if that eliminates the problem.

Thomas

...

[Ron]

If no luck with the above...

Sounds like it is too slow to begin with to me. There are two large humps on the motor. There are capacitors under them. Have them checked.
Some have a mechanism on the end of the shaft with a set of spring loaded weights that act as a switch to control the capacitor(s)... Make sure it is not froze up with dust/oil/etc.

[DMCMW Dave]

If no luck with the above...

Sounds like it is too slow to begin with to me. There are two large humps on the motor. There are capacitors under them. Have them checked.
Some have a mechanism on the end of the shaft with a set of spring loaded weights that act as a switch to control the capacitor(s)... Make sure it is not froze up with dust/oil/etc.

Yeah - I was thinking start switch (if it has one, not likely on a motor that small), or bad start capacitor.

[Stainless]

So I played around with it a little tonight. I took off the motor cover and drained all the air inside so there was no internal pressure. The compressor seems to start and run okay as long as there is no internal pressure when it tries to start. If I stop it after pressure is built up, it will sputter when I try to start it again. Here are some pics of what it looks like and a video of it running. Where do I go from here?
41584 41585


https://www.youtube.com/watch?v=oKS_lpl_row&feature=youtu.be

[content22207_2]

In the bad old days Craftsman used the same direct drive compressor on all its air compressors (my little 3 gallon hot dog compressor has the same compressor as the 30 gallon direct drive unit). If they're still doing that, just buy a little hot dog compressor and transfer the compressor to your tank. Should cost $50-$80 if you catch one on sale.

Bill Robertson
#5939

[David T]

The pressure switch usually has a little valve built into it to release the head pressure so the compressor can start easier. There is also a check valve in the tank between the compressor and the tank. The check valve holds the tank pressure back when the unload valve releases the pressure between the check valve and the compressor. If either valve fails the compressor will have a hard time starting against the pressure. Also if you have a low voltage condition it makes it hard on the motor. Check the voltage, the unload valve and the check valve. The valves may have to be cleaned or replaced. For a low voltage condition you may need to use a different circuit or call an electrician. If the whole house is low you may have to call the power company. Anything below 117 is too low.

[Ron]

...
If I stop it after pressure is built up, it will sputter when I try to start it again. Here are some pics of what it looks like and a video of it running.

Unclear/not enough info...
If you release all pressure then shut the drain (as in vid, I assume), what pressure does it go to before shutting itself off the first time? (If it is anywhere near normal, it could be the pressure switch allowing it to come on too soon.)
Does it seem ok for that first time only?

[Stainless]

Unclear/not enough info...
If you release all pressure then shut the drain (as in vid, I assume), what pressure does it go to before shutting itself off the first time? (If it is anywhere near normal, it could be the pressure switch allowing it to come on too soon.)
Does it seem ok for that first time only?

If I release all the pressure and turn it on and let it keep going, it goes until it automatically shuts off. I have it set to around 120 PSI, so it goes until it reaches that normal pressure. If I stop it before it reaches that pressure, like at 60 PSI, and try and start it again, it will just sputter. It does the same thing at full pressure. So it appears that it has issues at much lower pressures than just the normal 120 PSI. Thoughts?

[Ron]

Sounds like the capacitor(e) to me, even more.
They virtually turn the AC motor into a weak DC motor to get it going in the correct direction....A bad capacitor can make the motor fight itself....
I'd suggest removing them and taking them to a shop (eg Radio Shack tech). Be careful, they hold enough charge to destroy bone marrow...

[David T]

Sounds like the capacitor(e) to me, even more.
They virtually turn the AC motor into a weak DC motor to get it going in the correct direction....A bad capacitor can make the motor fight itself....
I'd suggest removing them and taking them to a shop (eg Radio Shack tech). Be careful, they hold enough charge to destroy bone marrow...

Refer to post # 12. Examine the pressure switch to see if it has that tiny unloader valve. If it doesn't then check the motor capacitors and start switch. Measure the house voltage.