Haier Mini spilt HSU18VC7 compressor runs for 5 minutes then stop 3 minutes then run another 5 minutes and so on.

This is called short cycling. It sounds like the compressor is getting hot and opening a bi-metal overload, which shuts the compressor off. The compressor cools, because it is not running and the bi-metal contacts close allowing the compressor to start again. This will repeat itself and is usually due to low refrigerant, which usually means there is a leak in the normally sealed refrigerant lines. The refrigerant cools the compressor windings and if it is low it cannot do that, hence the shutting off of teh compressor, cooling down process and restarting of your compressor. Short cycling will ultimately ruin the compressor.

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