ANTLIA AN-2021 compressor shaft locked

by David
(Scotland)

I have an ANTLIA AN-2021 21 Litre Air Compressor bought in Australia and brought with me when I had to return home to Scotland for family reasons.


I use it mainly for topping up the tyre pressures on two vehicles.

Was working fine until yesterday but now will not start.

When switched on (briefly) Motor just hums. Took off cover to check capacitor and found that direct shaft is locked.

Pressure is empty, condensation drained and oil level on red spot in sight glass.

How can I free it.

I am not very mechanically minded. Can you help, I am a pensioner and cannot afford to have it 'looked at' professionally.
Many thanks,

David Bowley (Lybster, Caithness,Scotland, UK KW3 6AT)

Comments for ANTLIA AN-2021 compressor shaft locked

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Oct 25, 2016
Pump Seized?
by: Ross Johnson

Direct drive compressors have an extended shaft on the motor onto which the compressor conrod is connected to the pump assembly. They are referred to as a close coupled unit.

If the sump of the pump became low in oil it could cause the lock up in the piston bore due to expansion caused by increased heat from lack of lubrication.

Compressors are a duty cycle rated product and cannot run continuously. They should be at rest for 60% of a ten minute period.

Most of these small units are overworked by their owners due to the low free air delivery from such a small pump which causes the overheating and subsequent seizure. This is contributed to by the exaggerations made by their respective manufacturers.

They also run at twice the speed of a belt driven compressor at 2850 rpm rather than via a pulley system with V belt.

Although China manufacture the largest majority of these there are still a number being manufactured in Italy and this brand may possibly be one of them.

Jun 16, 2016
ANTLIA AN-2021 locked up
by: Bill

By locked I am understanding that the pump itself is locked up, the motor shaft cannot therefore turn, and it's preventing the motor from starting.

The connection of the motor shaft to the pump must be removable, as it had to be assembled in the first place.

Can you see if you can separate the two and then, by trying to turn the motor shaft by hand, you can determine if it's actually the compressor motor that is seized, or the motor works fine when not connected to the pump, and it's the pump itself that's locked up?

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