Airmaster 15/60 start problem

[Ian Burden]

Just bought this and it runs well when tank has no pressure. When the tank is pressurised and I start bthe machine, the motor and compressor run slowly and then overload switch operates. If I release tank pressure, it starts and runs normally. Is it a simple fix, please?

 

[frank horton]

Sounds like the leak off /non return valve is stuck open...
Under the main on / off switch there’s a small plastic pipe...6mm ish o.d.....
Follow it to the tank fitting.....on this tank fitting there will be also a large pipe from the compressor head....
Anyway undo the large'ish brass blanking cap...poss about 3/4 or 19mm across flats.
Behind the cap u'll c a spring and a stainles flat washer....the washer closes the seat off....be careful not to loose the spring....only light gauge....
U'll normally find a peice off scale /rust....
Clean off and refit...should work ok....
Have had so that u need to do it twice as norm where there is some rusty bits about often there could be more...
This should sort it...

 

[rtbcomp]

Make sure the tank is empty before undoing any unions!

When it reaches pressure and cuts out do you hear a brief hiss, no hiss or a continuous hiss?

 

[Ian Burden]

Thanks. No hiss. The compressor cuts out at 150psi and will not restart without overloading until pressure is less than 50psi.

Frank - I tried your suggestion and the non return valve appears to be seating ok.

 

[rtbcomp]

Fill the tank and carefully undo the small pipe (unloading pipe) where it joins the non return valve.

The pipe between the pump and the tank (delivery pipe) will contain pressurised air so be careful.

If you get a short burst of air as the delivery pipe empties the problem is with the unloading valve on the switch or the unloading pipe is blocked.

If you get a constant stream of air the non-return valve is leaking too.

 

[rtbcomp]

^^ PS should add, make sure the compressor is disconnected from the mains before trying the above.

 

[Ian Burden]

I removed the end of the small pipe at the non-return valve end. - There was no sound of air. The tank remained at 150psi.

I appreciate your help. Do you have any further suggestions, please?

 

[rtbcomp]

OK. The non return valve will be OK, if there was no hiss the air in the delivery pipe probably leaked out slowly, suggesting a partial blockage in the unloading valve/pipe.

With the unloading pipe still disconnected, re-connect to the mains, switch on at the red knob and drop the pressure in the tank, if the motor starts OK and there's a stream of air from where the unloading pipe connects then the motor is OK and the port on the NRV isn't blocked.

Next thing I would do would be to re-connect the unloading pipe and disconnect it at the switch end and repeat the above, if there is air coming out of the unloading pipe then that is clear.

Be careful to point the end of the pipe away from you, if there was a blockage in the pipe, it could be expelled with some force! (Something to watch out for).

 

[Ian Burden]

I have tried this. thre unloading pipe is clear but when reconnected, the problem persisits.
Do you think that maybe the motor power is insufficient to overcome residual pressure in the tank? When there is pressure in the tank? The motor stuiggles and then cuts out except when the pressure in the tank is low. Should I suspect the capacitor?
Thanks again for your help.

 

[rtbcomp]

I think the problem will be in the unloading valve or pressure switch, if you don't get the hiss it isn't opening.

It should remain open until the pressure in the delivery pipe reaches about 20psi, which will give the motor plenty of time to spin up to speed. If the motor spins up OK with the unloader pipe disconnected I would suggest the motor is OK.

There are two things to looks for in the unloader valve, 1) is it blocked and 2) is it being pushed open when the pressure switch opens. It will have a plunger on it which is pushed down by a tag or similar on the switch mechanism.

 

[Ian Burden]

Thanks for your patience. In fact there is a loud hiss when upto pressure. will the problem still be in the pressure switch?

 

[rtbcomp]

Try switching off at the red knob on the pressure switch when it's about half full pressure, wait a few seconds and switch on again. You get the hiss and see if the motor starts.

Because the delivery pipe is empty there shouldn't be any pressure for the motor to work against.

Do you get the problem once the compressor has warmed up? Say after filling the tank 3 times?