Audi car heater is not hot (1). Check the connecting pipeline and radiator water tank: if it is blocked, it should be dredged and cleaned; When it is difficult to dredge and clean to normal, replace the pipeline or radiator water tank. (2) Check the water pipe and reset it if it falls off. (3) Check the fan. If the fan speed is too low or the air door does not return, repair the fan resistance block or adjust the air door to return. Check the fan motor. If it doesn't work, check its circuit and motor.