2010 Prius IV - when I have my ac system off and outside air on the system seems to heat the air to whatever the temperature was last set at? This should be a vent condition and air should be coming in from the outside even if the air outside is 50 degrees and the system was set at 70 when it was last on? The system seems to be heating this air. If I turn the system on and reset the temp lower, then turn the system off the air comes out cooler? Why is this?
First what do you mean by turning the AC system on and off? Do you mean the AC button on the Climate Control system? If yes, the system is still trying to maintain your temperature setpoint. On your example above, if your setpoint is 70 and outside temp is 50 it will attempt to heat the cabin temperature to the 70 setpoint. Likewise if you lower the temp setpoint below the cabin temperatue it will attempt to cool the cabin down to setpoint, with or without the AC on. This is an automatic Climate Control system not just a manual AC system. If you just want vent, select the vent position with the Mode button. The best thing to do is leave the system in Auto and adjust the temperature setpoint up or down to maintain your desired cabin temperature, fan speed, etc. The system is a really smart system that uses outside air temp and a sunlight sensor to help maintain cabin temperature.
Thanks for your reply. I meant the climate control system off. When the system is off - and the mode is on vent - why can't I just get outside air into the car nomatter what the temperature was at when it was in auto mode?
What I think you're explaining is the vent air comes into the car at a temperature you had the climate control set to before turning auto off. Yeah, it's a bit annoying but if you want air to come in at whatever temperature it is outside you basically have to set it to LO before turning it all off and making sure afterwards the vent setting is open.
AFAIK (but I could be wrong), I think the coolant flows through the heater matrix all the time and the heat into the car is controlled by the position of the vent flaps. The airflow is controlled and boosted by the fan when the Climate is on. When you turn the climate off the airflow vent position defaults to the floor and the heat flow (amount of hot air coming through) vent stays where it was. This means that when the car is moving the outside air flows over the heater matrix and down to the floor, the amount of heat flow depends on the previous setting (as you discovered) and the speed of the car. This is a good way of getting free heat in the winter, once the car is warmed up, as you don't have to turn on the climate, which uses electricity to power fans, vent flap motors and sensors. Also the ICE doesn't run as often if the climate is off, saving fuel. If it's an uncomfortable temperature, just turn on the climate momentarily, adjust the temp up or down, then turn it off again.
