I just noticed the body of my compressor was getting very hot, like too hot to touch, after only 5 / 10 minutes, which seems very wrong. Only other odd thing is that when it cuts out the motor on filling the tank it does another couple of stuttery turns of the motor, which isn't normal.

Any ideas about what to do? Are these serviceable? Does it need lubrication - I actually thought the things were "oilless"...?

It's pretty much like this one:

They are oiless, there's a coating on the cylinder walls , which over time wears out . That's probably why it's getting hot , there's too much friction on walls . Reading between the lines , you said body like where the motor is ? If so then there's something screwy going on with the motor . There's a thermal fuse inside that motor , if it keeps getting hotter it will blow the fuse and kill the motor . I don't think they are rebuildable . You could go to the manufacturers site and see if they have rebuild kits . But they probably want you to buy a new one .

These oil -less ones run and run- then stop, as Ed says they don't need lubrication and will get very hot in use.
In normal use they should be run for a few minutes then left to cool down, also try to leave the compressor in an airflow like a door/window. Last diaphragm compressor I had lasted 10 years, one last thing most low end compressors are made in same factory no matter whos badge is on it.

You could probably get the parts to rebuild it, but I'd lay odds that you could find a replacement cheaper - at least that's the way it is on this side of the pond.

Thanks, I thought you might all say that... Hard to get anything fixed for less than about the cost of a new one of these here in the UK as well, unless you do it yourself. I wonder what the coating is. Is it possible to open it and spray WD40 in it, since that dries, I wonder.
Stephen, is in a garage with the door open, and though it's been warm today, as you know, it could hardly be called hot, especially at 9 this evening!!

First of all, this type of compressor doesn't have a cylinder. It has a diaphram that flexes up and down, worked by a crank and rod on the motor. There is a one-way valve to keep the air going to the tank and not backing into the compressor. There is no lubrication. Most of the heat generated by any compressor is actually from compressing the air, not the motor running. You might need to look at the one-way valve, but I suspect that it may be the pressure you have it set at is too high or you need some airflow over the compressor head (the finned area) or the pressure valve is sticking. If it is the motor (possibly worn brushes), you might be better off getting a newer unit.
Hope this helps,
Norm S.

If the compressor is identical to the one pictured it's a piston compressor , not a diaphragm . So is the head of the cylinder hot or the body of the motor . Five minutes of running the motor should just be maybe warm .

I'm pretty familiar with this issue. The problem that you are having is a faulty/defective pressure switch. I believe the model number is BLPS-YKH or you can check the sticker. What is happening is that the switch is not holding the off position and thus the motor starts stuttering when it reaches the pressure and thats when the amperage of the motor sky rockets which causes the heat buildup. Do NOT use your compressor until you can replace or fix it. The high amp and heat on the motor may cause permanent damage to the coils. I remember buying the same pressure switch off eBay for around 15-19usd.

I encountered the EXACT same problem except with a dual piston version with a pressure release solenoid valve. During that time the motor would stutter and the solenoid valve won't activate.

Makes sense , hopefully no damage has been done .

Jomark, thanks for this advice, it sounds like you definitely recognise the symptoms. The pressure switch is this red plastic capped thing screwed into the side of the tank, and that has a split ring through the end? (edit: surely that is the safety valve...)

My compressor doesn't have a model number written on it, but I'm going to assume that not every compressor has a different pressure switch, so they should be interchangeable between similar looking compressors.

I will investigate further.

It's screwed into the cylinder head right between the handles . Pressure switch .

I just checked my previous order and the pressure switch model number is BLPS-YKH which is either a 43psi ON 57psi OFF or 3kg ON 4kg OFF switch.

I think this should be the same for your compressor. Even my compressor without the tank uses the same pressure switch (poor choice for a non-tank compressor really).

Also, I didn't buy it from eBay upon checking. It was from lelong.com.my a malaysian part seller site I think

Interesting topic, my compressor is identical to the one in original post (apart from labels) and behaves the same way ie; gets very hot and sometimes stutters/turns slowly after heating up. I use mine perched on the kitchen windowsill with window open to allow some extra cooling. I've had mine for a couple of years and although not used that often, perhaps once or twice a month, it hasn't failed yet.... although occasionally when using it for extended sessions I've had to leave it for 20mins to cool before it'll run again, not ideal but you get what you pay for!
The pressure switch is the one on the side of the compressor (black cover) the other on top of tank is a safety pressure relief valve (red cover).

You could put a fan on it , force the airflow to cool the motor . The plates at each end are removable . Maybe take a look inside , it could be dirty and might need a cleaning ?

I use this version (different labels as well)
http://www.tcpglobal.com/ABD-TC-28.html#.VYmFX0YpmnM

The main difference is that this one has a solenoid valve. When the pressure switch triggers, it also triggers the solenoid to release the air between the compressor and the flow valve right before the tank. This helps reduce the motor strain upon starting up. I am not sure why the single piston version does not have this release mechanism. When the compressor starts up with pressure still in the airline to the tank it produces a load that the motor will have to overcome which causes added heat buildup and in turn the motor will eventually start slower due to the heat.

I am assuming that firstcircles problem is the stutter upon reaching the pressure limit. You will hear a slight (sometimes inaudible) hum and a few clicks which sounds like sparks when this problem occurs and the motor starts to heat up rapidly. That means that the switch is engaged but not enough to supply the current required to turn the motor. The idle power being supplied to the non-running motor in turn increases the amperage and heat.

Can you add that ?

that's normal. Do not touch !! Check to make sure the moisture trap is fully closed or it will stutter etc..

Thanks to all, particularly Jomark who seems to know the technicalities of these devices. The pressure switch on mine doesn't have anything written on it (except a sticker that says '3'...) though the item you mention may well fit. When I web searched it, the same supplier in Malaysia came up, so perhaps that is their own model number. Couldn't see anyone in Europe selling these pressure switches on eBay, and 'Everything Airbrush' responded quickly to my question to say that they don't stock spares.

So anyway, I did what you do when you've got nothing to lose and disassembled the top end, and may have found the cause of the problem, which is corrosion. I now have a better understanding of why these compressors, although they work pretty well, are so cheap. The metal tube that runs vertically from the head of the cylinder down to the tank is steel and was quite rusty inside, to the point that I could knock lumps of rust out by poking through it. The cylinder head (with the fins on it) looks like some aluminium alloy and was corroded to the point that bits of fluffy alloy oxide was starting to creep into the aperture that the pressure switch screws into and into the end of the switch itself. Then when I took the plate between the head and the cylinder off, the piston sleeve had quite a bit of gunge hanging around on it.

I suppose all of that may restrict the airflow to the switch and / or be making the moving parts sticky. I cleaned it all up and gave it some WD40 and allowed that to dry before reassembling it.

A bit of an annoyance is that when I removed one of the allen bolts that holds the head on, a piece of what looked like swarf came out, but it was a piece of plastic coated wire that had been inserted in to the hole to make up for the fact that the thread had been drilled incorrectly or hadn't cut properly - in other words to repair a defect. Anyway, managed to get it back in with another piece of electrical wire. Probably not too critical, the pressure isn't that high, as witnessed by the piddly size of the allen bolts.

So all reassembled, I tried it out and it seemed OK - the motor kicked in and out sharply without any sign of a stutter and it didn't seem to be getting warm. Didn't use it for that long, but it was under the 300w halogen bulb on a pretty warm evening...

Some photos:

The front end off - did this to allow the pressure switch cable to turn while I was undoing it with a 14mm spanner, but not really necessary. To get the swich out it's probably better to take the head off and rotate that instead, while holding the switch body still with the spanner.


Under side of the cooling fins:


This is the top of the plate that sites over the cylinder sleeve and under the cooling finned head:

The white disk is a rubber valve that allows the air through - hence the marks around it. The white powder is corrosion dust from the head above it.

This is the top of the piston sitting inside the sleeve; note all the bits of corrosion dust and probably little bits of solidified lubricant.

Thanks a lot for putting that up, I may well give this a try with mine.

You have extended its lifespan .

What is the thread size of the pressure switch . You could find a replacement switch with that size thread and similar pressures , what's 3 and 4 bars into pounds ? I believe that's 40 and 60 psi .

Good to know that it is working so far. I did that once when I was troubleshooting the compressor and was able to fix it because i dropped and tightened the pressure switch and it unstuck the mechanism inside. Eventually my switch still gave way. You might have turned the pressure switch tight and fixed the issue like i did. Hope you could test it longer to make sure everything is fine.

Just Curious, how old is that compressor? The wear in the inside walls isn't supposed to happen even in prolonged use.

Edmund,
3 bar is around 43.5 psi and 4 bar is around 57psi the thread is 1/8. I was also thinking of getting a digital and adjustable switch in the future

I must of hit the submit button before typing .

That's what I was thinking off , maybe find one with an unloader , to drop the pressure before startup . You want the luxury version ? I believe it's just a snap disc and with wear and ultimately fail . Have another one ready . It's just good insurance .

Did you put this one back togethere ? How did it work afterwards ?