Anybody know about fixing air compressors?

[Mike Manning]

I have a chance to pick up a lightly used Makita MAC700 air compressor. Owner says when it's plugged in it "overloads". Trying to find out what exactly they mean by that but just wondering what you guys thought and how much trouble and expense could be involved in fixing something like that. Sorry to be vague but that's all the info I've got right now.

[Jerry Miner]

Pretty vague. Owner might mean that the start-up of the compressor trips the breaker in his electrical panel. Is it 110 volts? 220? Amp rating?

I once had a job-site 110v compressor that would trip breakers on start-up. I replaced the oil with 10w-30 and the problem stopped. Not saying this will work for you.

[Bill Dufour]

Cheap, high speed portable compressor. Not worth putting much into it. Probably bearings are shot or rings are sticking. If it overloads on starting with no pressure it is not the pressure relief valve failing to unload. Could be starting capacitor went bad.
Bll D

[Mike Manning]

Cheap, high speed portable compressor. Not worth putting much into it. Probably bearings are shot or rings are sticking. If it overloads on starting with no pressure it is not the pressure relief valve failing to unload.
Bll D

I realize I need to get more info. He does say he has used it three times over five years and it looks like it. But that's good to know.

[Nick Decker]

Might be cheap and portable but if it really hasn't been used much it might be something simple to fix. How much does he want for it? They're about $200 new.

[Curt Harms]

Cheap, high speed portable compressor. Not worth putting much into it. Probably bearings are shot or rings are sticking. If it overloads on starting with no pressure it is not the pressure relief valve failing to unload. Could be starting capacitor went bad.
Bll D

My question would be does it "overload" after it's been off for an extended time or while in use? A stuck unloader valve not opening would account for hard starting with air in the system. If it starts hard with no pressure, Bill's guess about bearings or piston sounds likely. MAC700s have a pretty good reputation AFAIK but there's always the exception.

[Darcy Warner]

Cheap, high speed portable compressor. Not worth putting much into it. Probably bearings are shot or rings are sticking. If it overloads on starting with no pressure it is not the pressure relief valve failing to unload. Could be starting capacitor went bad.
Bll D

Actually, they are a low speed cast iron pump.
Pretty dang good portable compressors.

[Bill Orbine]

Could be something as simple as pressure relief. One way to tell is to drain machine and then see if it runs. Otherwise, other problems could be more serious and may not be worth the trouble $$$ wise.

[Carlos Alvarez]

The assertions that it's a cheap high-speed compressor are just wrong. It's a half-speed compressor with a huge piston, and is rather quiet. Pretty sure it's also oiled, helping with noise. It's BIG for a portable, and the large piston size could easily cause it to blow a 15a break on startup.

How much does he want?

[Bill Dufour]

Actually, they are a low speed cast iron pump.
Pretty dang good portable compressors.

just took a quick look and assumed it was 3600 rpm since it is direct drive. Still 1800 is high speed to my mind. Good to hear it is cast iron. probably worth putting some money into then.
Might be rusted shut exhaust valves. If the intake is rusted shut it should still pump a vacuum no problem.
Does it rotate at all or just hum? Does it pump any air at all, build some pressure?
Bill D
I

[Mike Manning]

Got some additional info today but I have yet to see the compressor in person. Here's what I got from the owner...

"It was a great compressor. The quietest one I've ever used. Worked completely fine the few times I used it. Then all of a sudden I went to use it and it would pop breakers on the fuse box. I took it to a shop in Washington where I was living and they told me it was pulling too many amps. They said they could fix it for about 50$. I was in the middle of a moving and they didn't know when they could get to it."

Thoughts on what it might be and how confident you might feel about a fix? When I go to look at it what should I be looking for as indicators I need to just walk away from this compressor?

Thanks!

Mike

[Carlos Alvarez]

It's only $200 brand new, is it worth any effort or cost?

[Mike Manning]

The assertions that it's a cheap high-speed compressor are just wrong. It's a half-speed compressor with a huge piston, and is rather quiet. Pretty sure it's also oiled, helping with noise. It's BIG for a portable, and the large piston size could easily cause it to blow a 15a break on startup.

How much does he want?

It is oiled and he wants a Grant for it.

[Nick Decker]

See if it'll start on a 20 amp circuit.

I tend to agree with Carlos. A new one is about $200. Why give him even half of that if it might be a problem? I'd be reluctant to offer $50.

[Mike Manning]

See if it'll start on a 20 amp circuit.

I tend to agree with Carlos. A new one is about $200. Why give him even half of that if it might be a problem? I'd be reluctant to offer $50.

What if I could get it for $25?