Since this is at least the second time I have noticed this I thought I would post to see if anyone else has had the same issue. I almost always drive with my climate control set to OFF (Fan is off, recirculate is set to off - as in let fresh air in from the outside). My climate temp setting is set to 74 for the very few times I will turn on the climate control system. The outside air temp (according to the Toyota gauge) was 66 degrees this morning when I was driving to work. As usual, I turned on HV mode after I got up to freeway speeds and drove about 12 miles at speeds above 70 MPH. When I was about 2 miles from my freeway exit, I noticed I had about 18% EV charge left so I decided to swap to EV mode (not EV Auto btw) for the last few miles on the freeway. About 30 seconds or so later, I noticed hot air coming from the vents. Then I looked down and could literally see my EV charge melting away. I think I used about 15% charge for the last 2 miles (there is a slight uphill grade on the freeway before hitting the exit). I then checked my climate control settings to verify everything was off and it was. I then took a look at the energy diagram (the one that shows the car, engine, climate control, battery, etc.) and it did NOT indicate any energy flowing to the climate control system as it would if the system were active. I made it to the freeway exit with about 3% EV left. That same distance at freeway speeds should only have used up a max of about 5-8% EV but instead it used up more than double that amount. It is obvious that the climate control system was running even though the display indicated that it should have been completely off. The warm air seems to be coming from the vents (Fan is OFF) when I swap to EV mode from HV when exiting the freeway. When it happened the first time I just assumed some hot air from the engine was being caught by the open intake vents. From what I observed today, it looks like the heat pump was working in some kind of stealth mode. Anyone experience something similar? Thanks!
Well something "similar" will happen with almost every vehicle on the road......but maybe not for the same reasons. When you turn the "heater" off it is never really off because some heat "leaks" into the system from the engine or where the sun shines on the vent intake or from a damper door that leaks a bit of air. If you turn the fan on just one notch, it might evacuate that heat out of the ducts in a few seconds and then blow mostly outside air.......might not too.
I also typically drive with climate control OFF, I do however make sure that the temp is at the LO settings before doing so, reason: in my Gen3, during the winter time, i set the air to ~ 73 and turned the climate OFF during my commute (50 miles), the cabin got enough heat through the vents to keep me comfortable and not running the fans, during non-winter, temp was set to the lowest. While I have not been able to reproduce the exact behavior in my Prime (has not been cold enough to need heat ), I'm for now assuming it works the same way ... do you know what your temp was set to? if it was the previous for AC use, eg 75, at 66 outside it would warm up the cabin ...
Actually the climate control system is never really off. In "off" it's actually still in "heat". Even without a fan running, air will circulate on the highway, and it will be heated if your setting is 74 and outside it is 66. Turn the heat setting down and you won't get warm air coming in, just outside air.
Thanks for the info. I had left my temp setting at 74 for the air conditioning (cooling). It doesn't really get cold enough to run the heat very often in SoCal. I always thought "OFF" meant off but it looks like it means something completely different with a Prius So, conversely, if my temp setting is 66, will the A/C circulate cool air through the vents if the outside temp is say, 80? (Assuming the fan is off and climate is OFF as before) ? It would be nice to simply be able to tell the climate control to not heat/cool anything unless I tell it to. Running the heat pump when you don't want it on kills my EV range.
I have not observed that ... feels more like outside temp ... but usually i have the windows cracked ...
Air is cooled only if "A/C" light is on (well, almost only - it can be cooled if defrost is on too). If you turn that light off the air coming through the system will be at whatever temp. its source is. This being said, the cowl gets warm in the sun, so to begin with you will get warm air until the ducts cool off to ambient (if outside air is being used). This also confused me a while ago. I thought "system off" meant "off", but it turns out you can't turn off the heat with a switch. You have to set the temp. low enough heat isn't called for. Think of it as a legacy car where you have to turn a knob counterclockwise to mechanically block the coolant from the heater core (from my experience with my FJ Cruiser). So it's a good thing you can adjust the temp. from the steering wheel too.
Thanks for the explanations! TBH, I didn't know the temp was adjustable from the steering wheel. Time to RTFM a little closer I guess.
changing temp from the steering wheel was a function on the Gen3 Prius, not sure if it's on a Gen4 but not available on the Prime
@Db17 - Yeah much easier. Seems ridiculous that the heat comes on even though you have everything set to off.
One of the coolest things in the Prius is the air conditioning system. I don't see why anyone would choose not to use it. Firstly it provides a way of conditioning the air optimally conditioned to preserve and maintain the battery. Secondly it filters the air and keeps it warmer or cooler than the ambient air outside. Thirdly it keeps you from destroying the nearly flawless aerodynamics of the vehicle. Read up on it some learned about how it calculates how much glass there is and how much heat the vehicle is observing due to the amount of glass and the temperature of the outside air adjusting the mixture of heating and air it is really amazing. Then have your ear automatically filtered and conditioned for you at the temperature that you most enjoy and watch how your gas mileage actually improves.
Myself, I'm not big on using any kind of climate control if I can keep the windows cracked open. At freeway speeds, I keep two windows open (driver and rear passenger) and that is only 1/2" each in order to keep the aerodynamic penalty as low as possible. I had nano ceramic tinting installed in order to reduce the amount of incoming heat (and it works very well). Admittedly, when it gets up into the 90's outside, I will definitely be using the A/C - hey I'm not crazy
Still, read up on it and you'll be rewarded with a longer battery and better gas mileage too iPhone ?
