The insulation "3azl" of old fiat cars is very bad, you find air coming 2 you from every where, if u want 2 put air conditioner ok no problem but u must make very good insulation first.
Take care also of the condition of your motor " el motor tamam wala ta3ban?" because the air conditioner will need a strong motor - good luck.
Sorry I have only an English key board.
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