Verified answer

This is one of the few times I would suspect a low charge right away. It sounds like the low pressure switch is doing it's job and keeping the unit from self destructing. Call a tech and have it checked. In this case, I believe you do have a refrigerant leak.

Al

Any more most residential air conditioners do not have low pressure switches. Even if it was the low pressure switch there would not be enough refrigerant pressure to even make the switch to allow the unit to start.

Three seconds is just about the amount of time for the compressor to get up to speed and then drop out when it switches over to the run windings. I would recommend you call an HVAC tech because it really sounds as if the run windings are out on the compressor.

could be a bad run capacitor,if it just started doing this i would check the freon level and if it's an old unit you might be able to get by putting a hard start kit on it but i would have a professional check it out and go from there.the hard start kit is usually the last alternative and if that don't work then you know what comes next.if the compressor is bad see what the cost of putting a new compressor in would be.depending how good the condition of the unit is in

It sounds like to could be a relay or the compressor. if it is low freon it will stay on but will not cool. also check your motor make sure your compressor is not over heating. most likely time for new unit.

It sounds the unit is tripping on a low freon indication. have a tech come out

and check the charge on your unit.