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?

[Nick Decker]

Sure, I'd take a chance for $25. The guy needs to realize that it's barely worth anything if it doesn't work.

[Ryan Liegel]

I'd go for it at $25 or $50. If he took it to someone who would fix it for $50, I'd assume that means the needed part isn't very expensive, especially if you repair it yourself.

I've got this model and it's been smooth running, quiet, and reliable for me for about 5 years now. Kinda heavy compared the the cheap pancake ones, but I'd probably get the same one if I were doing it again.

[Mike Manning]

The owner says that the compressor won't start. As soon as you try to start it, it overloads and trips the breaker. Any thoughts/ideas on what could be causing that? And are they easy and cheap to fix?

[Jerry Bruette]

Could be a discharge valve is stuck shut, dead heading the compressor.

[Mike Manning]

At the PO's garage, the instant we tried to turn the compressor on it tripped the circuit. Any ideas about how to diagnose a problem like this?

Oh by the way, I brought it home with me. The thing looks brand new. He was the original owner. Says he used probably 3 times in the 5 years he had it until it stopped working.

[Brice Rogers]

"they could fix it for $50". They probably think that it is either the capacitor or the dump valve.

[Nick Decker]

I think my first call would be to Makita. They might be able to at least point you in the right direction.

[Bill Dufour]

I would remove the outlet check valve and leave it disconnected then try to start the motor.
Bill D.

[Curt Harms]

At the PO's garage, the instant we tried to turn the compressor on it tripped the circuit. Any ideas about how to diagnose a problem like this?

Oh by the way, I brought it home with me. The thing looks brand new. He was the original owner. Says he used probably 3 times in the 5 years he had it until it stopped working.

That to me points to the unloading valve. I had an inline unloading valve stick open after an extended period of no use. A tap 'fixed' the problem and it's been fine since.

[Mike Manning]

To complete this thread, I bought the Makita compressor for $20. After a couple of failed attempts to troubleshoot it not starting (and tripping the circuit breaker), Makita suggested I take it to one of their factory service centers. The nearest one to me was in Dallas. A couple of weeks ago I went to visit my mom in Fort Worth and dropped it off to get it diagnosed (at no charge) in hopes it would be a $40 fix. The Makita tech called to let me know the electric motor was fried and would need to be replaced - $129 total cost. I asked for a day to think about it. I called the next morning and asked if there was any way he could do it cheaper. As expected, he said he couldn't. When I said I couldn't justify spending that much on it he said "hold on", paused for 10 seconds and then told me he would fix it as a warranty issue. They even shipped it back to me in Austin at no charge. I've never had to send any of my Makita hand tools for servicing but what a great first experience! Kudos to Makita!

PS I also learned that contrary to what the previous owner told me (5 years) the air compressor is less than two years old.

[Mike Manning]

Oh, one last thing, do NOT run a Makita air compressor on an under-powered extension cord and never on a cord longer than 50'. FYI. This from the service tech.

[Carlos Alvarez]

Oh, one last thing, do NOT run a Makita air compressor on an under-powered extension cord and never on a cord longer than 50'. FYI. This from the service tech.

Never run ANY motor that way. Simple as that. Low voltage is deadly. Current must rise as voltage goes down, causing more resistance, reducing voltage further, driving the current up, causing more resistance......

The length is not relevant as long as the wire gauge is correct. Remember that your house is on an "extension cord" that is many miles long.

[Nick Decker]

Thanks for the update, Mike. Good on Makita.

[Carlos Alvarez]

Good on Makita.

Actually this just shows us that the service center, which is usually an independent shop, is willing to lie and steal. They tried to get max cash from the end user first. When that failed they settled for the warranty repair credit by doing a repair they knew they should not do under warranty. They are liars and thieves, and I'd avoid that shop at all costs.

This is all no different from walking into a Makita warehouse and stealing a new motor.

[Mike Manning]

Never run ANY motor that way. Simple as that. Low voltage is deadly. Current must rise as voltage goes down, causing more resistance, reducing voltage further, driving the current up, causing more resistance......

The length is not relevant as long as the wire gauge is correct. Remember that your house is on an "extension cord" that is many miles long.

Thanks Carlos! I only use 12 gauge extension cords anymore.

[Mike Manning]

Actually this just shows us that the service center, which is usually an independent shop, is willing to lie and steal. They tried to get max cash from the end user first. When that failed they settled for the warranty repair credit by doing a repair they knew they should not do under warranty. They are liars and thieves, and I'd avoid that shop at all costs.

This is all no different from walking into a Makita warehouse and stealing a new motor.

This was NOT an independent shop Carlos. It was THE Makita factory service center. I could have taken it to an independent shop in San Antonio which was 200 miles closer (round trip). I chose the MAKITA factory service center because they'd give diagnose the failure at no charge. I didn't check to see if the independent shops would do the same. The mileage was a non-factor as I've mentioned my mom lives within 25 miles of the service center.