If the indoor temperature can't be lowered, is there a fault with the air conditioner?

You can first test whether the air outlet and outlet air temperature of the air conditioner are abnormal. If it is normal, it means that the air conditioner has no fault. The reasons why the indoor temperature can not fall down may be caused by too many people in the room, excessive heat dissipation, high outdoor temperature, room windows not closed tightly, curtains not tightened, heat source near the air conditioner, frequent door opening and closing, etc.