by Matt
(Ohio)

Dear Bill,

My air compressor worked just fine until I decided to lay it on its side (which I didn’t know you shouldn’t do) then it started smelling bad after about 10 minutes, so I shut it off. I then stood it upright and let it sit for 24 hours, then I turned it back on.

Kobalt 26 gallon air compressor
Kobalt 26 gallon air compressor
Kobalt 26 Gallon Oil Free Air Compressor Wont Start 21891171
Kobalt 26 Gallon Oil Free Air Compressor Wont Start 21891171

it smelled bad again and shut off on its own. It won’t power back on.

I don’t know much about air compressors, but I know how to rebuild electric motors and engines, so I thought I would tear it apart.

No leaks in any of the airlines and I attempted to drain the tank, but nothing came out anyway.

First thing I noticed was the electric motor stator was burned and dirty, but the motor piston looked great. Here is what I have done, and my compressor still won’t turn on.

1. Completely disassembly motor and piston housing.
2. Cleaned piston, housing, everything inside and then lubricated piston and housing.
3. Cleaned the stator with Emory cloth until brand new and polished look came back, also cleaned and leveled out the brushes. (Brushes are only about 1/2″ in length, seems short) Brushes carry continuity from brush to wire hookup.
4. Re-assembled entire electric motor and head assembly, everything moves freely, smells great and looks great.
5. Did a continuity test from the end of the power cord all the way to the electric motor and all circuits are complete.
6. Did a continuity test on the pressure switch and it is passing along power.
7. When I plug the compressor into the outlet I have 109V at the electric motor, testing right at the brushes. When I turn the Auto/On switch to on the volts jump to 120V, I have the pressure knob turned all the way up (have tried assorted options) and the motor never kicks on.
8. This is the end of my expertise and would appreciate any help you may provide.

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Is this the 99007 ?
by: Doug in s.d.ca.

Lots of trouble with these.

It’s oilless, so being on its side really shouldn’t bother it.

Speaking of bother – does it not strike you as odd that you saw 109V on it before it was turned on?

Where was that measured?

Are you sure there was continuity through the brushes at the time you turned it on? I’m not sure about the brush length, but maybe they aren’t making good enough contact to carry the current, and went open?

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Kobalt 99007
by: Matt

Dear Doug,
It is the 99007 and I did find it odd that the motor always has 109V going right to it. I measured this at the Positive and Negative Wires attached the brushes right on the motor. I had 109V with the main switch turned to Off, when I turn to On/Auto it jumps to 120V, I thought maybe that was normal but I guess not. Any ideas what else to check, I guess I don’t know why the electric motor isn’t spinning even with voltage.

Matt

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Kobalt 99007
by: Matt

Dear Doug,
I tested the Voltage right at the motor positive and negative wire then again at the Carbon Block Brushes, so I know voltage is getting through the carbon block brushes. I just don’t know enough about these to figure out why the electric motor won’t start if it’s getting voltage. There is no Start Capacitor or Reset button that I can see on this motor.

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It’s aka VLK1582609
by: Doug in s.d.ca.

K. Let’s get some basic stuff cleared up –

Forget the compressor for a moment, and check that outlet. If you probe round ground to the narrow blade, you should see 120V.

From ground to the wide blade should read zero. And if so, you can plug a toaster or heater in there, and it works? If yes, fine. (But don’t skip the voltage checks, please.)

If that’s all good, then we go back to the compressor. Plug it in and turn it to on.

If it doesn’t run, check the voltage from ground to one side of the motor. You should get either close to zero volts or close to 120 volts. Now check the voltage on the other side of the motor. That should be the opposite of the first side – either near zero or close to 120, whichever the first side was NOT.

If you have 120 on both sides of the motor, then the neutral wire is broken somewhere. Follow the wires back to neutral. (one will go 120, so if that’s where it goes, then the other one is supposed to go to neutral, so follow that one)

Tell us what you find.

BTW, there is an overload switch in the motor, but it’s *supposed* to reset itself after cool-down.

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Kobalt 99007
by: Matt

Doug,
I’m slightly confused about the Voltage Testing, I’m no pro but I did pass my county electrical certification. This unit is 120V, the motor has 3 wires attached to it. White (Neutral), Green (Ground) and Black (Hot Wire). If I put the meter Probes 1 on the White wire and 1 on the Black wire I get 120V. Although I didn’t understand testing Ground To Neutral and Ground to Hot I did it anyway and it produced Zero Results. So, I get 120V at the motor with the On switch to ON, the motor does not have an overheat Reset switch anywhere on it, any other reasons why it’s not starting?

Thanks

Matt

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Voltages
by: Doug in s.d.ca.

I want to make sure the outlet itself is wired correctly. Sounds like it probably is.

There is no visible reset switch. It is internal to the motor, and self-resets, unless it’s failed.

Let’s look at it a little differently – OHMS.
Unplug the unit, switch to the ON position, and short the blades together for a second or two. There may be a slight arc. That’s OK. Set the switch back to OFF.

Now, test for resistance across the blades of the plug. With the unit switch in the OFF position, it should show open, infinite resistance. Ditto from the narrow blade to the round ground.

Now, turn the switch back to ON. You should still have infinity between the ground pin and either blade.

But *across* the blades, you should have something pretty close to zero. You may get a bounce from the capacitors when the meter is first connected. That’s normal, wait for it to settle down. If that still reads infinity, or nearly so, then the either the motor itself is open, or the overload switch is not resetting itself, or the brushes are not making contact.

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Kobalt
by: Matt

Doug,
Yes the outlet is fine, did what you said and the On/Off switch is working fine, what’s next.

Matt

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On/Off switch is working fine, what’s next.
by: Doug in s.d.ca.

One of us is glossing over something. If what we checked is as I specified, it should either work, or blow fuses, or at least hum. Any of that true?

To recap, you’ve put the ohmmeter leads across the blades of the plug, and with switch OFF you get infinity, and with switch ON, you get nearly zero, correct?

You should be using the lowest scale; what is the reading in ohms, switch ON?

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Kobalt
by: Matt

This test was taken from the prongs on the power cable, Neutral & Hot wire. I guess i’m confused, isn’t this On/Off switch a standard switch, it either has continuity or it doesn’t. Also, I am getting 120V at the motor, doesn’t this mean everything is working except the motor?

Switch On 00.50 Ohms
Switch Off 00.34 Ohms

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Kobalt won’t run
by: Doug in s.d.ca.

Please tell me the resistances for the switch on/off are transposed.

Something is way screwed up here in a way that makes no sense. But it *must* be made sense of.

So, let’s try this:
Disconnect both wires from the motor.
Do the switch test from the plug blades again. It’s open regardless of the switch position, right? If not, specify.

Now, connect the wires that were going to the motor together. Do the plug test. Now it’s open when the switch is off, and zero or real close to zero ohms when the switch is “ON”, right? Again, if not, specify.