150 l 220vac air compressor hums on restart

by Tobias
(South Africa)


When I start the unit up from scratch, ie no air in tank, it start perfectly and builds up pressure to the cutoff point with no problem.

Then I use air......When the unit reaches the refill pressure point, it tries to start and the motor turns three or four times and them sits and hums. If I drain the tank completely, it starts up again correctly to the switch off pressure point, on second startup, it does the same things, motor turns a couple of times and the hums

Hope you can help

Best regards

Comments for 150 l 220vac air compressor hums on restart

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Aug 08, 2014
Humming air compressor
by: Bill

Hello Tobias.

In the troubleshooting section there is a page of information about why air compressors hum on restart.

Two things to check right away. Is the unloader valve working? If not, get that fixed. See that page on this site for info.

If the unloader valve is working then your next check is the start capacitor. See how to do that on the page on this site as well.



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