Question about winter air conditioning, or not...

<div class='quotetop'>QUOTE(dulcimer @ Dec 5 2006, 07:31 PM) [snapback]358272[/snapback]</div>

Same thing as defrost, the AC removes the water i.e. Humidity and the heat exchanger adds heat after that. Just put it in defrost or defrost and vent does the same thing automatically and with better control. Let the Car do it for you! Set it and forget it!

 

As Henry said, the A/C will remove humidity, aiding in defrosting the windshield. However, it should not be necessary once the engine is warm and the vents are putting out hot air.

The A/C does use electricity (several amps worth) and that electricity ultimately comes from gas. I imagine the gas used is measurable but not large. Obviously, you don't need the A/C to get heat, and in fact the A/C will reduce the amount of heat you get. Use it for a quick defrost and then turn it off.

Cracking a window open a bit and/or selecting fresh air will also help reduce fogging.

 

This is what I do: set the temperature to 76F. Then push OFF button to turn off everything. While driving around the car would bring in all warm air. Engine doesn't seem to kick in if doing that way. Of course I won't be too warm if I stuck in traffic.

Question: is there any way to change temperature when fan is off?

 

In case it wasn't obvious from the posts above, the A/C button with the bar above it is for the air conditioning compressor. The compressor is the refrigeration part of the system, and completely unrelated to making cabin heat. When you turn off the compressor, the climate control system cannot cool the interior of the car, other than venting in outside air. The cold from the compressor also serves to dehumidify the cabin air, so an air conditioning compressor is sometimes run in cold weather along with heat to better defrost the windshield, but it is usually not necessary.

Most of the confusion comes from Toyota's double use of the term A/C or air conditioning. They call the entire climate control system air conditioning, which it is technically, and then turn around and use the abbreviated form A/C for mechanical cooling, which is how we normally use it in the USA. It's a common source of confusion.

So remember, when you touch the button and turn off the bar above A/C, it's just the cooling compressor that gets switched off.

Tom

 

<div class='quotetop'>QUOTE(Clar @ Dec 7 2006, 05:45 AM) [snapback]358808[/snapback]</div>

Unfortunately no.

 

<div class='quotetop'>QUOTE(dulcimer @ Dec 5 2006, 10:31 PM) [snapback]358272[/snapback]</div>

I think you mean for heat? I do the same, turn the heat on low set the temp and them turn the air off and when you drive, the temp will come out of those vents warm. If its 30 degrees out, it doesnt do the trick, but if its brisk it works fine and YES I have seen an increase in MPG doing it this way on those not so cold days.

 

<div class='quotetop'>QUOTE(savegreenbacks @ Dec 7 2006, 09:02 AM) [snapback]358911[/snapback]</div>

I leave mine on auto, just set the temp and forget it.

 

<div class='quotetop'>QUOTE(bhaynnes @ Dec 7 2006, 01:19 PM) [snapback]358922[/snapback]</div>

Exactly!

 

If you have not had auto climate in a vehicle before, it takes some getting used to. However, auto climate in vehicles has been around for at least 40 years now and has evolved quite significantly. However auto climate in the Prius is no different in behavior as compared to the systems in Buicks and Mercurys which I have driven in the past. In general, these systems operate best when you put them into full auto and specify an interior temperature (set it and forget it). Why, you ask.

Simply put, the auto climate system is designed to hit your target set point the most effective and expedient way possible. That is a combination of air volume and air output point. When you have a vehicle interior and it is 30 degrees and you have a setpoint of 70 degrees, you have a 40 degree differential the system needs to make up. The programming of these systems will call for a huge air volume and will place most of the air output to the floor vents. Then as the vehicle starts to reach your setpoint the fan speed will drop and the vehicle may change the outpout from floor to a mix of floor and dash vents.

In general, the vehicle starts out its heat cycle by not actually activating the fans in the system for a couple of minutes while waiting for the engine to heat up. Once there is some base line level of heated coolant to cycle through the heater core the auto climate will fire up the fan and put the air output on the floor. The system will spool up the fan to one of the highest settings to move a great deal of warmer air volume into the cabin. The system starts out with the air on the floor because a high volume of air directed at the floor with be more comfortable for the passengers, and since heat rises, it is better to heat the floor and let the heat rise to the top.

As the setpoint is reached in the cabin the system will lower the fan volume and may move the air to a split between floor and dash. Now that the heater core is up to temperature, moving the air up to the dash vents won't be uncomfortable for the passengers and will help to maintain cabin warmth better.

I hope this makes sense and is useful in helping understand the system's logic?

 

<div class='quotetop'>QUOTE(Tideland Prius @ Dec 6 2006, 08:20 AM) [snapback]358718[/snapback]</div>

I thought I read somewhere that the heat was electric rather than from the engine as in other cars. Is this incorrect?

EDIT
I did some more reading and apparently it has both. Never mind.

<div class='quotetop'>QUOTE(Clar @ Dec 7 2006, 09:45 AM) [snapback]358808[/snapback]</div>

If the fan is off, then isn't the A/C or heater off too? I believe that the temp. will be the outside temp. (as in strictly "vent"). If you want to change the temp., then you need to turn on either the A/C or heater.

Does anyone else have info to validate or dispute this?

EDIT
I did some more reading and apparently it does affect the temp. Never mind again.

 

<div class='quotetop'>QUOTE(PA @ Dec 27 2006, 09:55 AM) [snapback]367215[/snapback]</div>

Most of the above is incorrent, at least in my 2004.

While there is some heat provided by electric, it is very small, and only at the floor vent and only under certain conditions. I think (but am not entirely sure) that it's only if the heat is set to maximum when the car is cold. Almost all the heat actually provided to the cabin comes from the engine's waste heat.

There is indeed no way to change the heat temperature when the fan is off, but there is some air flow even with the fan off, at least if the vent is set to outside air. The A/C will be off, so no cooling will be provided. However, if the temp setting was left higher than the cabin temp when the fan was turned off, then some warm air will come out the vents. if you do not want this warm air (e.g. it's now warm outside) you must turn the fan on, then turn down the heat temp, and then turn the fan off again.

This is one of my big peeves against the car.

I much prefered the climate control on my old Civic: One knob to turn the heat up or down; another knob to switch from outside air to recirculated air, with all gradations in between (e.g. a little outside air) and another knob to select the vents.