compressor on the blink

[123hotchef]

it seems my compressor dont like working too hard!
I was using it for blasting with the pressure pot for the first time today when I noticed the problem.

first it over heated and the thermal cut out needed to be reset

But then it started acting strange the motor would try and start and stop then it would try and spin a few times then stop then try again this kept going on it was quite near being full not far off the 150psi when i found what it was doing.

I let it cool down turned it back on and it was fine but i didnt blast anymore.

What should I be checking? it is a old snap on compressor 1999

 

[rtbcomp]

The thermal cut-out opening is not necessarily an overheating problem. It's called a thermal cut-out because an over-current situation heats a wire which causes it to expand and operate the cut-out, that said the motor running too hot will also trip the cut-out due to external heating of the device.

It sounds like the pump may be getting too hot and binding, is there enough oil in it? Is the compressor out in the open or in an enclosure?

 

[123hotchef]

The thermal cut-out opening is not necessarily an overheating problem. It's called a thermal cut-out because an over-current situation heats a wire which causes it to expand and operate the cut-out, that said the motor running too hot will also trip the cut-out due to external heating of the device.

It sounds like the pump may be getting too hot and binding, is there enough oil in it? Is the compressor out in the open or in an enclosure?

I did think it could be pump related it is a belt driven pump. It's under a bench and the oil is full possibly a little over full it is also newish oil I put in last year

 

[pedrobedro]

Check the unloader valve is working. It sounds like the pump is still under tank pressure and the motor is stalling.

 

[123hotchef]

Check the unloader valve is working. It sounds like the pump is still under tank pressure and the motor is stalling.

ah funny you should say that the unloader valve was never working when I purchased the compressor second hand the pipe was cut and plugged, probably because it was faulty, it has never been a problem before now. I guess I could fix the unloader valve not sure how they work or what they consist of though

 

[merryman]

the motor would try and start and stop then it would try and spin a few times then stop then try again this kept going on it was quite near being full not far off the 150psi when i found what it was doing.

Are you sure it was the motor and not just the compressor starting and stopping? Sounds a lot like the belt slip we used to get on our old work compressor when the belt needed adjusting, always worse when it got hot.

 

[123hotchef]

Are you sure it was the motor and not just the compressor starting and stopping? Sounds a lot like the belt slip we used to get on our old work compressor when the belt needed adjusting, always worse when it got hot.

no i was watching the motor if the belt was slipping i would have seen the motor running continuously

 

[rtbcomp]

ah funny you should say that the unloader valve was never working when I purchased the compressor second hand the pipe was cut and plugged, probably because it was faulty, it has never been a problem before now. I guess I could fix the unloader valve not sure how they work or what they consist of though

Have a look under the pressure switch, or better still post a photo. You can get unloader valves, there are two type, a) delayed and b) non-delayed. You need the delayed type because they close after pressure has built up to about 20 psi in the delivery pipe, the other type closes almost immediately.

You will probably find it's easier to replace the whole pressure switch rather than faffing about trying to get the correct unloader.

It works by opening when the pressure switch opens and empties the delivery pipe of air so next time the motor starts up it does so under no load. You will need to make sure the non-return valve is working too.

 

[123hotchef]

Have a look under the pressure switch, or better still post a photo. You can get unloader valves, there are two type, a) delayed and b) non-delayed. You need the delayed type because they close after pressure has built up to about 20 psi in the delivery pipe, the other type closes almost immediately.

You will probably find it's easier to replace the whole pressure switch rather than faffing about trying to get the correct unloader.

It works by opening when the pressure switch opens and empties the delivery pipe of air so next time the motor starts up it does so under no load. You will need to make sure the non-return valve is working too.

ill grab a few pics later or tomorrow all clean now

 

[123hotchef]

View attachment 147318 View attachment 147319 View attachment 147320

Have a look under the pressure switch, or better still post a photo. You can get unloader valves, there are two type, a) delayed and b) non-delayed. You need the delayed type because they close after pressure has built up to about 20 psi in the delivery pipe, the other type closes almost immediately.

You will probably find it's easier to replace the whole pressure switch rather than faffing about trying to get the correct unloader.

It works by opening when the pressure switch opens and empties the delivery pipe of air so next time the motor starts up it does so under no load. You will need to make sure the non-return valve is working too.

Here we go some nice pics

 

[123hotchef]

 

[123hotchef]

surely if the compressor has filled up most of the way and the motor starts stopping and starting i wont be the unloader then will it?

 

[WorkshopChris]

Have you given it a good sniff?
Just wondering if you have cooked the start winding.

 

[123hotchef]

Have you given it a good sniff?
Just wondering if you have cooked the start winding.

yes mate no burning it is working ok now it has cooled down didnt like being used for sand blasting!

 

[brightspark]

blasting constantly realy over heats most compressors unless there old type slow running .running a direct drive constantly can cook a new one in half an hour

 

[123hotchef]

looks like i need a bigger compressor!

 

[rtbcomp]

I've fitted an extra fan to mine. The fan in the pulley blows most of the air across the crankcase so I've set the new one slightly higher to blow air across the head & barrel. It runs all the time the mains is on, not just when the compressor is running.

Extending the inlet away from the motor prevents warm air being drawn in.

 

[123hotchef]

I've fitted an extra fan to mine. The fan in the pulley blows most of the air across the crankcase so I've set the new one slightly higher to blow air across the head & barrel. It runs all the time the mains is on, not just when the compressor is running.

Extending the inlet away from the motor prevents warm air being drawn in.

i guess it is worth a go too, do u think the unloader needs sorting I dont think this is the problem but i am no expert

 

[pedrobedro]

The unloader is there for a reason and is to take strain off the motor. Fix it before you do anything else just to rule it out.

 

[123hotchef]

The unloader is there for a reason and is to take strain off the motor. Fix it before you do anything else just to rule it out.

Complete new pressure switch looks the easiest option