Fairly sure we had this model on our last boat. We have a later model on the current boat. From memory on the previous one, I am fairly sure you need the switch to the flame symbol. Then dial round to get the temp desired - for start up, put it on a high heat. If the green light is coming on, then obviously you have power to the controller. You should then immediately be able to feel a cold draft coming from the outlets - very gentle one. This may go on for several minutes as the system primes up. You can normally also hear the diesel pump clicking (slow steady click) on the heater unit. After a while, it will sound like a jet engine is starting up and the fan speed will increase and you should start to feel warm air. Its similar on the our present one, just a faster sequence and more options to regulate the heat. No timer though.