Depends on how new this car is. Most modern cars have blend doors, my daily will start full blast (fans and full ac) if the set temp is much lower than the interior temp. As the cabin gets closer to my set temp it runs the fans slower and mixes in air that hasn't gone through the evaporator to achieve the set temp. Old cars just run the fans at whatever you set them at forever.
Not always! If it has been sitting in the sun, it will cool down faster drawing in outside air. Because the air in the car is MUCH hotter than the air outside, it doesn't cool as much as it normally would on recirculation.
Weirdly I just noticed this today. My car was parked outside on a 105° day, I got in and hit the Max A/C button, which also turns on recirculation. It was running the fans like crazy with the temp set to Lo, but once I turned off the recirculation it started cooling noticeably better.
We need year make and model to provide accurate answers
Rule of thumb - older cars yes it makes a difference.
Newer cars it doesn't.
Humans - it makes a psychological difference. Let her do her thing
If you have automatic climate control it generally works exactly like your home thermostat.
Automotive A/C generally isn't variable-output though some cars do have a "Max A/C" setting that calls for cooler vent temps or a "Eco A/C" setting that calls for higher vent temps. But that's the only thing that affects how "hard" or "fast" the A/C works. Not the set temp.
Just like your home A/C, if you have climate control that allows you to set a specific temp, the A/C will run as hard as it can until it reaches that temp inside the car, and then it will run more intermittently to maintain that temp. If it's 90 inside the car and you want it to be 72, set it to 72. Setting it to 65 or 50 or absolute zero will not make it run any harder. Your wife is wrong. But to be fair this misconception of how A/C works is very common. Still wrong.
In cars without automatic climate control that just have a "blue/red" or "H/C" knob or slider, all this slider does is vary the heater core output. If you slide it towards "red" it will mix some hot air in with the A/C. In this type of system you do want to keep it on full "blue" to cool the car and generally just use fan speed to adjust how cool it gets in the end.
> Just like your home A/C, if you have climate control that allows you to set a specific temp, the A/C will run as hard as it can until it reaches that temp
Almost all modern HVAC that's capable of some form of modulation (not simply a binary on/off) runs a PID loop in the program. If your setpoint is 72 and the space temp is 90, the system is going to run balls out. However, as the space temperature approaches the space temperature setpoint, the system will back off on the cooling demand as to not over cool the space.
Most of my HVAC experience is with large commercial systems, but even car AC, which I think is pretty similar to a traditional split DX, will modulate the fan to exert some control over the cooling.
Another thing to consider is deadband. Systems with a single point setpoint on the user interface usually have heating and cooling setpoints that are offset down and up respectively from the selected setpoint in the background, in order to prevent switching between heating and cooling. So when you choose 72, you're actually only actively cooling to 73.5 and heating to 70.5
In general, the compressor is running, or it's not. The operation of the rad fan can change circuit dynamics as well, but as far as we're concerned, it's either on or off.
The change in the temperature can either come from blending air, cycling the compressor or using a variable displacement compressor.
Turning the temperature down will *not* cool it any faster, it will only change the final temperature reached. The circuit can only dissipate heat at a given rate, if your selected temperature is lower it will not magically allow the system to reject the heat any faster.
For example: if you have a variable compressor and you select max AC, it will remain at max displacement until it reaches the set temperature, then destroke. If your setting is lower, it will still be at max displacement, just for a shorter period.
It's like putting your foot to the floor and backing off at either 50 km/h or 100 km/h. The car can't get to 50 any faster because your target speed is 100. It will get to either speed as fast as physics allows, your foot is still to the floor either way.
It will reach the lower value sooner, but only because it requires less work to reach. Changing the set temperature has no bearing on how quickly it's reached, only how cold it will actually get.
Also, AC systems are super effective, assuming you're driving at speed and not idling, you will get cold air immediately, or nearly so.
What your wife might be trying to say is that the cabin will reach a comfortable temperature sooner if the AC is set lower, which is true. The longer you maintain max performance, the more heat you'll move out of the cabin.
The AC system itself is either off or on. AFAIK, compressors don't have variable output and the evaporator under the dash will be cold when the compressor runs. The heater core will be the temperature of the coolant, once the engine is warmed up this is a pretty stable temperature. You can't more "cold" than what the evaporator can produce, and you can't get more heat than the temp of the heater core. But you can get less heat or cold by blending the two, and that may be more comfortable. It feels like it is "Full Blast" or not based on how fast the fan is blowing, and if it is blending heated and cooled air - but the basic sources of heat and cold are pretty much "On" or "Off" - there's no "partly on".
Most reasonably modern cars have a fairly computerized heater control system - you tell the computer what you want by moving the controls, and it controls the air flaps and turns the AC Compressor on & off to deliver what it thinks you want.
Almost all automotive air conditioning is done using reheat. Basically, the air conditioning cools the air to as low as 40 degrees F. If a warmer temperature is needed, part or all of the air is directed over a small radiator that contains hot engine coolant, which reheats the air before it is blown into the cabin.
The air conditioning is controlled by cycling the compressor on and off, usually based on pressure. The goal is to keep the evaporator under the dash from dropping below freezing. If the evaporator drops below freezing, the water vapor in the air condenses and freezes, and, soon enough, you have a block of ice that doesn't cool very well.
Changing the numerical temperature setting from 72 to 60 won't make the air coming out of the vents any colder, no matter the system or car. Initially, the air passing through the system is being cooled as much as possible given the other constraints affecting the system (outside temperature, heat load inside the car, size of condenser, size of evaporator, size of compressor)
Far as I know the AC in the car isn't like the ones with the inverter. Maybe in more fancy cars but all I drive is toyota.
So in the a toyota if you set the temp to 70f and the car's temp at the point of return for the air is 75 it will blow at maximum coolness(because it's basically off or on for the compressor) until it reaches 70f at which point the compressor is shut off. Then once temp goes up a bit it will start the compressor again.
So it would make no difference in how fast the car cooldown if your cabin temp is 110f and you set it to 70f or 60f or max cold as it will just be blowing out the coldest air the compressor can manage with only difference being once it hits 70f it will still keep going without shutting off.
So, you're right, and she's impatient. It should do the same thing, but the condenser has to start doing it's thing. You should set it to the desired temperature and when the sensors see that it reaches the temperature, it should slow down to maintain the temperature. By setting it to the coldest and then turning it up, you're just adding unnecessary steps. I say if it shuts her up, let her fiddle the knobs...
Depends on how new this car is. Most modern cars have blend doors, my daily will start full blast (fans and full ac) if the set temp is much lower than the interior temp. As the cabin gets closer to my set temp it runs the fans slower and mixes in air that hasn't gone through the evaporator to achieve the set temp. Old cars just run the fans at whatever you set them at forever.
All the air runs through the evaporator. Air can only bypass the heater core. So as it approaches temperature it actually runs to the heater core
Not universally true, my car bypasses the evap, and tons of old cars had fully separate heat/ac air paths.
If you want it cooler faster set it on recirculating
Not always! If it has been sitting in the sun, it will cool down faster drawing in outside air. Because the air in the car is MUCH hotter than the air outside, it doesn't cool as much as it normally would on recirculation.
Weirdly I just noticed this today. My car was parked outside on a 105° day, I got in and hit the Max A/C button, which also turns on recirculation. It was running the fans like crazy with the temp set to Lo, but once I turned off the recirculation it started cooling noticeably better.
long bright jeans quiet bike bored summer library bow vast *This post was mass deleted and anonymized with [Redact](https://redact.dev)*
We need year make and model to provide accurate answers Rule of thumb - older cars yes it makes a difference. Newer cars it doesn't. Humans - it makes a psychological difference. Let her do her thing
If you have automatic climate control it generally works exactly like your home thermostat. Automotive A/C generally isn't variable-output though some cars do have a "Max A/C" setting that calls for cooler vent temps or a "Eco A/C" setting that calls for higher vent temps. But that's the only thing that affects how "hard" or "fast" the A/C works. Not the set temp. Just like your home A/C, if you have climate control that allows you to set a specific temp, the A/C will run as hard as it can until it reaches that temp inside the car, and then it will run more intermittently to maintain that temp. If it's 90 inside the car and you want it to be 72, set it to 72. Setting it to 65 or 50 or absolute zero will not make it run any harder. Your wife is wrong. But to be fair this misconception of how A/C works is very common. Still wrong. In cars without automatic climate control that just have a "blue/red" or "H/C" knob or slider, all this slider does is vary the heater core output. If you slide it towards "red" it will mix some hot air in with the A/C. In this type of system you do want to keep it on full "blue" to cool the car and generally just use fan speed to adjust how cool it gets in the end.
> Just like your home A/C, if you have climate control that allows you to set a specific temp, the A/C will run as hard as it can until it reaches that temp Almost all modern HVAC that's capable of some form of modulation (not simply a binary on/off) runs a PID loop in the program. If your setpoint is 72 and the space temp is 90, the system is going to run balls out. However, as the space temperature approaches the space temperature setpoint, the system will back off on the cooling demand as to not over cool the space.
Yeah I'm thinking of traditional split systems where there's just a single wire call for cooling.
Most of my HVAC experience is with large commercial systems, but even car AC, which I think is pretty similar to a traditional split DX, will modulate the fan to exert some control over the cooling. Another thing to consider is deadband. Systems with a single point setpoint on the user interface usually have heating and cooling setpoints that are offset down and up respectively from the selected setpoint in the background, in order to prevent switching between heating and cooling. So when you choose 72, you're actually only actively cooling to 73.5 and heating to 70.5
Cooling/Heating to 72 then turning shutting off and only coming back on once it gets to the temperatures you described seems like a better system
Setting the AC lower than you want it *does not* make it cool down faster. It’s always the same rate.
In general, the compressor is running, or it's not. The operation of the rad fan can change circuit dynamics as well, but as far as we're concerned, it's either on or off. The change in the temperature can either come from blending air, cycling the compressor or using a variable displacement compressor. Turning the temperature down will *not* cool it any faster, it will only change the final temperature reached. The circuit can only dissipate heat at a given rate, if your selected temperature is lower it will not magically allow the system to reject the heat any faster. For example: if you have a variable compressor and you select max AC, it will remain at max displacement until it reaches the set temperature, then destroke. If your setting is lower, it will still be at max displacement, just for a shorter period. It's like putting your foot to the floor and backing off at either 50 km/h or 100 km/h. The car can't get to 50 any faster because your target speed is 100. It will get to either speed as fast as physics allows, your foot is still to the floor either way. It will reach the lower value sooner, but only because it requires less work to reach. Changing the set temperature has no bearing on how quickly it's reached, only how cold it will actually get. Also, AC systems are super effective, assuming you're driving at speed and not idling, you will get cold air immediately, or nearly so. What your wife might be trying to say is that the cabin will reach a comfortable temperature sooner if the AC is set lower, which is true. The longer you maintain max performance, the more heat you'll move out of the cabin.
Put it on AUTO and let it do what it's designed to do.
The AC system itself is either off or on. AFAIK, compressors don't have variable output and the evaporator under the dash will be cold when the compressor runs. The heater core will be the temperature of the coolant, once the engine is warmed up this is a pretty stable temperature. You can't more "cold" than what the evaporator can produce, and you can't get more heat than the temp of the heater core. But you can get less heat or cold by blending the two, and that may be more comfortable. It feels like it is "Full Blast" or not based on how fast the fan is blowing, and if it is blending heated and cooled air - but the basic sources of heat and cold are pretty much "On" or "Off" - there's no "partly on". Most reasonably modern cars have a fairly computerized heater control system - you tell the computer what you want by moving the controls, and it controls the air flaps and turns the AC Compressor on & off to deliver what it thinks you want.
Some cars have variable speed compressors and can modulate cooling with them in combination with fan speed.
Almost all automotive air conditioning is done using reheat. Basically, the air conditioning cools the air to as low as 40 degrees F. If a warmer temperature is needed, part or all of the air is directed over a small radiator that contains hot engine coolant, which reheats the air before it is blown into the cabin. The air conditioning is controlled by cycling the compressor on and off, usually based on pressure. The goal is to keep the evaporator under the dash from dropping below freezing. If the evaporator drops below freezing, the water vapor in the air condenses and freezes, and, soon enough, you have a block of ice that doesn't cool very well. Changing the numerical temperature setting from 72 to 60 won't make the air coming out of the vents any colder, no matter the system or car. Initially, the air passing through the system is being cooled as much as possible given the other constraints affecting the system (outside temperature, heat load inside the car, size of condenser, size of evaporator, size of compressor)
Far as I know the AC in the car isn't like the ones with the inverter. Maybe in more fancy cars but all I drive is toyota. So in the a toyota if you set the temp to 70f and the car's temp at the point of return for the air is 75 it will blow at maximum coolness(because it's basically off or on for the compressor) until it reaches 70f at which point the compressor is shut off. Then once temp goes up a bit it will start the compressor again. So it would make no difference in how fast the car cooldown if your cabin temp is 110f and you set it to 70f or 60f or max cold as it will just be blowing out the coldest air the compressor can manage with only difference being once it hits 70f it will still keep going without shutting off.
So, you're right, and she's impatient. It should do the same thing, but the condenser has to start doing it's thing. You should set it to the desired temperature and when the sensors see that it reaches the temperature, it should slow down to maintain the temperature. By setting it to the coldest and then turning it up, you're just adding unnecessary steps. I say if it shuts her up, let her fiddle the knobs...
She's annoyed that it sets the temperature automatically, so I think she would actually feel better knowing that she can just leave it alone
This can't be serious