AC & heat controls

The short answer is put it in Auto and set the temperature where you want it and it will be fine. You can still turn the AC on or off while in Auto. You may also need to turn the defroster on or off. Leaving the climate control in Auto will not have a noticeable impact on mileage as long as you don't have the AC on and the temp set to super cold.

There are some older posts here where we discussed the Gen 3 climate control settings in excruciating detail but you will most likely need to use Google to find them if they still exist. There is also some limited information in the owner's manual.

 

You might note that when in "Auto" mode the system will default to "Recirculate". This is so the cabin air is not blended with outside air. The purpose is to make optimum use of the HVAC system to keep the A/C compressor and ICE from operating trying to keep up with outside temperatures.

 

I read in the other thread that if you are in "recirculate" mode with AC on, the air could develop musty smell... so I either move it to "outside air" mode or I turn off the AC a few minutes before I reach home.

This musty smell isn't Prius specific, my other cars have the same musty smell if the vent is left in "recirculate" mode with AC on for a long period of time.

 

If the evaporator drain is clear I don't see this as a problem. Most of the time when a musty smell developes it is when water ( condensation ) gets trapped in the evap. housing.

 

Adjusting fan speed will turn on the fan and set it at the speed indicated. It will also turn on A/C sometimes. A/C means air conditioning, meaning heating or cooling, as required. Set your desired temp. If you set it to 65F and it's lower than that outside it will only blow outside air into the car. Until the car gets too cold, then it will heat the air. Use "Auto" for best results.

In winter you absolutely want outside air. This is to decrease the humidity in the car so the windows don't fog/ice. If you use "Auto" it will not decrease the mileage noticeably. It will start on recirc. but will then go to outside air when ready. If you turn on defrost (front) it will run the A/C (cooling) to dry the air and will use outside air. It will heat the air and blow most of it on the windshield.

The cabin air filter is behind the glove box. Empty the glove box (if you don't it will empty automatically on the floor when you do the rest here ). Open the lower glove box, press the sides in so the little "ramps" clear the dash, unhook the "damper" and the glove box will pivot down out of the way. You can see the filter on the firewall. Pull it out and look at it. If it's plugged clean or replace it. If not put it back in and replace the glove box.

 

I *think* this is true only when you have the air conditioner on. I find that I don't need recirc past the first five minutes or so, and I usually turn it off. For some reason, the fan becomes less noisy when recirc is turned off.

 

No. It will still try to control the temperature to whatever the setting is. The only way to guarantee pure "vent" is to set the temperature to the lowest setting, turn the A/C off, and ensure that the vent is not set to one of the defrost settings (which turns A/C on, even though the light stays off). In general, any time the temperature is set to lower than the interior temperature and A/C is off, you get vent - the max lo temp setting just covers the case where it's already really cold in the cabin.

I think usually it's most efficient at recirculate, assuming that the interior temperature is closer to the desired temperature than the exterior temperature is. (In other words, if your car was baking in the sun at 150°F and you turn on A/C, you're better off on fresh air for a few minutes, until the interior temperature is below the exterior temperature again.) In cold weather, recirculate keeps all the humidity from your breath in the cabin, so it's often preferable to use fresh air, which is drier and won't fog up the windows as easily. Once the car has had time to fully warm up, heating with fresh air won't make a difference, since the excess heat is a waste product otherwise.

Assuming you just set Auto to whatever temperature you can tolerate (and disable A/C if you don't need it), it will be more efficient than many ways you might manually manipulate it; for example, setting the temperature to 68° with A/C on and the fan on 1 bar is way less efficient than setting it to 78° on auto with the A/C on, even if the cabin temperature is 68° in both cases.

If you want to let cool air in, just turn the temperature down below what the temperature is inside. In your example, if the cabin is 80°, it won't heat at all, even though the outside temperature is lower than the set temperature - the set temperature is a goal for the cabin, not the temperature that is coming out the vents. On the other hand, if the eventually drops to 69°, then the car will add a little heat to keep the outside air from cooling it below your set temperature.

Bottom line; just set the temperature to whatever makes you comfortable. Bonus efficiency points for leaving A/C off, and for leaving the heat off until the car is fully warmed up - this may take 20 minutes or more. (I live in a mild climate, and it takes ~4-6 miles of city driving, or maybe 2-3 of highway driving, when outside temperatures are around 50° or so.)

Heat goes to your feet, cooling goes to your face, and defrost goes to defrost. This is generally preferred - otherwise heat to your face leaves a big pocket of cold air at your feet. On the other hand, my face and hands are more sensitive than my feet, so sometimes I don't care if my feet are frozen solid...

If you have the solar ventilation system, clean it every 10,000 miles, and replace it every 20,000. If you don't, clean it every 15,000 miles and replace it every 30,000. That's what the manual recommends, anyway. If you use the climate control a lot, or in very dusty or dirty places, it might need it sooner. If you don't, then the recommendation may be more often than you need to.

 

I've been trying to remember that the recirc button is also on the steering wheel. For me, having recirc on the wheel is handy because I like to turn on recirc when I'm behind an old car with bad exhaust. Or a big dust event or some other noxious outside force.