Clarke Champ Frame Compressor Fault

[Andrew Hart]

Hi guys, I have a 110v Clarke Champ frame compressor that I have a strange fault with.

Basically, it randomly struggles to run up to speed, but only sometimes. The problem is worse the colder it is. If the outside temperature is 25c or above it doesn’t do it. When I turn it on, sometimes it buzzes and turns slowly, gradually getting faster. Very often this takes the 20Amp overload out. I wait for it to cool down for 30 seconds or so then try again. After 2 or 3 tries it normally starts and runs up to pressure fine. In normal use when it is cutting in and out frequently, it then starts fine as long as it is still warm. If I leave it a few hours to go cold, same problem. The weird thing is if I take the cover off and turn the motor fan by hand it turns easily. If I take the load off the compressor by taking the discharge pipe off the cylinder head, it starts and runs fine every time. I run the compressor off a 3.3kva transformer.

Here is what I have done so far to try and diagnose the fault:

1.) Changed the oil using the correct grade.
2.) Cleaned and subsequently replaced the inlet filter.
3.) inspected the piston, rings and bore which are immaculate.
4.) inspected the check valves in the cylinder head which are fine.
5.) inspected the non-return valve with the rubber seat where the discharge pipe enters the receiver.
6.) Replaced the pressure switch and safety valve.
7.) Replaced the 60uf motor starting capacitor.

I am struggling to think of anything else to try with this. Can anyone think of anything else to try? This is a great little compressor 95% of the time, it’s just a pain in the ar$e the other 5%!

I can post a link to a video of the fault if that helps.

TIA

Andy

 

[Dcal]

I had a similar problem on my compressor.
It turned out the belts were slack which I wasn't expecting.
Certainly worth checking.

 

[Andrew Hart]

Unfortunately it’s a direct drive compressor so no belts. Thanks for the reply

 

[Dcal]

Have you an amp meter? The type type that clamps over a cable? (needs to be a live or neutral not both at the same time)
It's worth checking the current draw when the compressor is starting normally and when it' struggling.

There will be an unloader valve somewhere which will dump the air in the head and line to the tank so the compressor isn't starting under load.
There could be an intermittent fault in that part of the system.

 

[Andrew Hart]

Here we go, pictures speak a thousand words:

Watch “Clarke Champ Compressor” on Vimeo:

 

[Dcal]

There's something wrong with the unloader circuit.
It should get up to speed before it tries to make pressure.
when you remove the outlet pipe is there a puff of air?

 

[Andrew Hart]

I can’t find any sort of unloader valve in the system at all. There are 2 plate type non return valves in the head, the spring loaded non return valve on the receiver and the normal safety valve. What would prevent this compressor starting under load which seems to be the problem?

 

[Andrew Hart]

Video of removing outlet pipe at pressure:

Watch “Clarke Champ Compressor” on Vimeo:

 

[WorkshopChris]

Do you have a multimeter with a capacitor test setting?

 

[Dcal]

There must be something that lets the air out of the compressor head and pipework when the compressor switches off (when it up to pressure.
It might be in the pressure switch but you can usually hear a blast of air when it switches off.
If the non return valve is leaking back it will cause the same issues.

 

[Dcal]

you can hear the blast of it unloading in the video.
Did it start up fine the next time after you put the pipe back on?

 

[Andrew Hart]

Do you have a multimeter with a capacitor test setting?

Yes, it measures 58uf. I have also changed the cap and it made no difference.

 

[Andrew Hart]

Here is a video of it running fine when the discharge pipe is reconnected. As I said, when it gets beyond its first start and keeps warm it’s usually fine. The colder the ambient and colder the compressor, the worse the problem

Watch “Clarke Champ Compressor” on Vimeo:

 

[Andrew Hart]

you can hear the blast of it unloading in the video.
Did it start up fine the next time after you put the pipe back on?

Yes it definitely blasts from the pressure switch when up to pressure.

 

[Andrew Hart]

This is a parts list for the air side. I can’t see an unloader valve. I assume that means it’s integral to the pressure switch. As I said, I have replaced the whole pressure switch assembly, but I suppose it could be faulty again?

 

[Dcal]

When it's hard to start see if it's got air in the outlet pipe.

I think the motor is ok as it starts all right when off load but it might be weak.

You are certainly going about it in a methodical way to fault find.
My best guess is the air is leaking back from the tank to the head.

 

[Andrew Hart]

When it's hard to start see if it's got air in the outlet pipe.

I think the motor is ok as it starts all right when off load but it might be weak.

You are certainly going about it in a methodical way to fault find.
My best guess is the air is leaking back from the tank to the head.

I’ll let it cool down and check later. I had thought about putting a manual dump valve on it to overcome the problem, but I don’t like bodging stuff. It is something really simple but it’s got me totally stumped. Really appreciate the input though, it’s good to bounce ideas off other people.

 

[carbon]

Was the capacitor you replaced near 60uf

 

[Andrew Hart]

Was the capacitor you replaced near 60uf

Yes an identical capacitor. If a start capacitor is knackered you would get the buzzing and struggling to start but it wouldn’t be intermittent unless it was a bad connection. Capacitors either work or they don’t in my experience.

 

[Andrew Hart]

When it's hard to start see if it's got air in the outlet pipe.

I think the motor is ok as it starts all right when off load but it might be weak.

You are certainly going about it in a methodical way to fault find.
My best guess is the air is leaking back from the tank to the head.

it doesn’t look like air is leaking back past the check valve and it looks like the unloading valve in the pressure switch is working, as there was no air in the discharge pipe when it tried to start:

Watch “Clarke Champ Compressor” on Vimeo: