Help needed with compressor

Hi. My air compressor is playing up and I need some advice. Its a belt driven 2.5hp, 50 litre job - newish but just out of warranty. It wont build up the pressure. When it runs, the pressure stays at about 50 psi - doesn't go down, doesn't go up. It seems to be making a softer sound then before - different.

What happened was that I was using it today when it started pumping and failed to turn off automatically when it hit 10 bar. I switched it off and played round with it for a bit, switching it off and on etc. Then I was called away for about an hour, thinking I had turned the compressor off. I hadn't, and when I came back it was running and had been for quite a while (I think) because it had a burnt smell and was extremely hot. I must have left the power on accidently and when the pressure got low (there is a slow leak in the line) it switched itself back on - and stayed on till something burnt out - or something like that.

Any advice on what most likely failed ? How to fix it ? Is it straightforward to take the head off and simply have a look ?
My own googling seems to indicate that the reed valve is a likely point of failure. Is there any way I can check this before going any further ?

cheers
Arron

Sorry to say that the 'burnt smell' probably means your motor windings have suffered. The likely cause is that a) the starting capacitors in these motors are crap and age really quickly (they last about the time of the warranty) and b) the motors are not designed for continuous duty and overheat and c) the capacitors and started windings are not meant to be started frequently - like more that 20 times an hours or so.
If your reed valve didn't seal properly for some reason and the switch stayed on, the motor possibly overheated. You then switched it on and off repeatedly adding to the problem with a weak capacitor by overheating the start winding as well. So when the motor started by itself in your abscence with cooked windings, it no longer ran at full speed and cooked properly......
You may well find the reed valve worn, bent or chipped, but I suspect that your motor is cactus as well..... sorry.... :C

Was the smell electrical or mechanical.

Most compressor pumps are rated at a low duty cycle so dont like to run for long periods especially these newer aluminium pumps, the old cast iron pumps could handle the extra running better.

If it has been running for a long period the motor should not have been a worry but because it was not turning of the pump overheats and then the valves and rings over heat.

You indicate that it is still running ok but wont build up pressure which indicates the motor is ok but the pump may need an overhaul.

New rings valves, valve springs and hone the cylinder as this will be glazed from the continual running.

While mucking about get a new pressure switch.

Quote:

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Originally Posted by Jim Carroll

Was the smell electrical or mechanical.

Most compressor pumps are rated at a low duty cycle so dont like to run for long periods especially these newer aluminium pumps, the old cast iron pumps could handle the extra running better.

If it has been running for a long period the motor should not have been a worry but because it was not turning of the pump overheats and then the valves and rings over heat.

You indicate that it is still running ok but wont build up pressure which indicates the motor is ok but the pump may need an overhaul.

New rings valves, valve springs and hone the cylinder as this will be glazed from the continual running.

While mucking about get a new pressure switch.

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It would be cheaper to get a new better quality compressor in the long run.
The chances of finding someone willing to do the repair work and get the required parts would most likely be problematic

It's not working so if pulling it apart won't make things any worse, you might even get lucky and find it is a simple issue to rectify. If you can't repair it (unlikely) keep the tank and use it to add air capacity with the new compressor you will need to buy. The problem might be in the air pressure/switch controls and it might not be in the pump itself.

Well I've just bought another compressor so I dont need to hurry fixing this one. I paid about $700 for the broken one so I dont really regard it as a cheapie - but maybe I'm wrong.

The motor seems to be running at the same speed as before so I dont think the windings are toast. I'm hoping the compressor head just got cooked. The head has 6 or so allen-key headed screws. Are there any issues with just removing these screws, popping the head off and having a look? After I've had a look I can go from there.

Cheers

I had a very similar problem with my Bunnings cheap compressor some 12 months ago. I was almost glad to see it malfunction as I was looking for an opportunity to get a better unit

Anyway it would only get up to ~60 psi and so it could not switch off so the motor was overheating and it would then stop working.

It turned out to be the head gasket had a crack/leak. The head gasket on mine was made from a thin piece of Aluminium so I cut a new one out of aluminium sheet and much to my annoyance it's been working perfectly again

OK, I'm updating this just in case someone with the same problem reads this post in the future.

So after not doing anything about this for 6 months I finally got the time to fix it. I took the head off and went to Gosford Power Tools with it. Very helpful fellow on the counter listened to my story and took one look at the head to check the valves were in good shape, then said 'gasket blown'. I pointed out that there was no leakage from the gasket but he said he'd repaired hundreds of these in the past and they were almost always a blown gasket - but leaking internally. He took it out to the workshop, prised the valve plate off and yep, blown gasket. Couple of dollars worth of gasket material later, its working like new.

cheers
Arron

Noting you picked this correctly, BobL :;