Hitachi AC Breakdown of motherboard within 4 months – no replacement

My Hitachi AC has died within 4 months of purchase. Motherboard is faulty. I had called up customer-care immediately to register complaint. Service team picked up the unit. It has been 3 weeks, the only response i have received so far is we don’t have replacement part available. How long am I supposed to wait? This is a new unit purchased. Why cant the service team find the replacement part? Why are such AC units being sold in the market if replacements parts are not available? Really regretting purchasing a Hitachi AC!!!

Hitachi AC Faulty ac brand new Hitachi split

Bought ac from Hitachi 3days back, defective product ,never functioned properly, installation team told remote is faulty then after remote replacement told two cards are faulty,I am not ready to accept this faulty ac at any cost
I paid for a new ac and don’t have a need to accept the faulty ac for the cost of new.if no prompt action is taken,legal course will be my wayout