Compressor overload keeps tripping

Bruce Wingate

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I have a Kobalt 60 gallon, 240v compressor with very little use (<10 hours even though it is 3 years old). Fitted it up the other day and it built pressure slowly and stopped before max pressure. Ran maybe 20 minutes. The next day I let it run venting so no pressure built up and it ran for 20 minutes or so. Did it again today and it ran for 10. Each time I let it chill down and hit the reset switch.

The motor never got very hot. I could touch it easy but maybe not for long

Service call was made, but is there anything simple i can look at in the meantime?

Thanks
 

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Make sure you are getting 110v to both legs, not just one.
 

Vbb199

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Verify the integrity of the pressure switch plus a clean 110v on each side
 

Vbb199

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Right off the bat, you could pull the pressure switch cover, turn the compressor on, and watch it as it pumps up, see if the magnetic contacts on the switch engage at the same time its cutting off.

They may be improperly shimmed

There's many youtube videos on checking pressure switches on well pumps.... or air pumps.... what have you

Assuming you own a multi meter

If you don't, or you do not feel comfortable digging in to electricity, please call a professional

I feel like I must state that disclaimer. I would hate to see someone harmed on my watch over the internet
 

Bruce Wingate

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@Vbb199 - thanks. I go slow with electricity but I'm mostly OK with simple checks and fixes.
 

Bruce Wingate

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The tests for the switches didn't make sense to me so I replaced the pressure switch and the results were the same.
 

Vbb199

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Did you check to see if you're getting a fairly balanced 110v on each side ?
 

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All the OP needs to do is verify there is 220-250 volts across the two wires. That said, if the compressor has been working for years, the problem probably has nothing to do with the power source.

Please let us know what the problem was.
 
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Bruce Wingate

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Did you check to see if you're getting a fairly balanced 110v on each side ?

All the OP needs to do is verify there is 220-250 volts across the two wires. That said, if the compressor has been working for years, the problem probably has nothing to do with the power source.

Please let us know what the problem was.
Sorry I'm slow in responding, although I would like this fixed, I have other things that are more urgent.

I checked both power leads and get 125 and 122 on them. That is with a multimeter connecting the leads to the ground screw.

The compressor worked last year although I only used it a little - there were no changes to the set up. I don't really have enough experience with this compressor to know for sure, but it sounds like it is running slow. (It is definitely running - I'm not getting a no-start with a hum like with a capacitor failure.)

After the compressor runs and stops and I let it cool down, it won't restart unless I press the reset switch.
 

Bruce Wingate

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Now my line of thinking is that the centrifugal switch is stuck on so that the primary windings (starting windings?) are overheating. Now I just have to locate that switch and figure out how to test it.
 

Bruce Wingate

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I thought I had this with the Pereira relief valve. Disconnected the pipe from the head to the tank and the compressor ran for about ten minutes and it sounded faster, but then it tripped the overload switch. But this time the compressor motor got hot. Not too hot too touch, but not comfortable to hold for too long.

Now the motor starts and stops relatively quickly. Now I'm letting cool for a while to see what happens when it's cooler. Next I'll be checking the capacitors
 

Bruce Wingate

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I thought I had this with the Pereira relief valve. Disconnected the pipe from the head to the tank and the compressor ran for about ten minutes and it sounded faster, but then it tripped the overload switch. But this time the compressor motor got hot. Not too hot too touch, but not comfortable to hold for too long.

Now the motor starts and stops relatively quickly. Now I'm letting cool for a while to see what happens when it's cooler. Next I'll be checking the capacitors
"Pereira" relief valve = pressure relief valve, that's some autocorrect madness.

So, I called a local electric motor repair shop to see about testing the capacitors (I don't have a proper multimeter for that) and he said that it wouldn't be them and to check the amperage to the motor.

I didn't do that mostly because I didn't understand it too well.

I disconnected the belt and took all the load off the motor and it ran for 15 minutes and tripped the thermal overload. Any suggestions on where to look next before I call the shop back? They were nice enough, but sounded like they didn't want to deal with it.
 

Vbb199

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Is there a bearing that is seized somewhere perhaps ?
 

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Well you know it's a motor problem if it tripped with the belt off. Is the motor hard to turn with the belt off. Should spin freely.
 

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