What should I do if the Elantra hot air cannot be adjusted?

The heater water tank is blocked. Elantra hot air can't be adjusted. The heater water tank may be blocked, so it can be cleaned. Elantra's warm air uses a blower to blow the heat from the warm air small water tank into the cab. If the air volume is insufficient or the distribution of cold and hot air is uneven, the heat of the small warm air tank will not be radiated, and the temperature of the warm air will not come up.