AC Cooling Time

Joined
Aug 9, 2022
Messages
144
Is it normal for the AC system to start blowing "cool" air out of the vents pretty much immediately, but take about 5-10 more minutes before it is "ice cold"? I hooked up manifold gauges to it before, and found that the high and low side pressures were within specification.
 
Is it normal for the AC system to start blowing "cool" air out of the vents pretty much immediately, but take about 5-10 more minutes before it is "ice cold"? I hooked up manifold gauges to it before, and found that the high and low side pressures were within specification.
I say yes...It also dependent on temp and humidity...the more humid the longer it takes because the AC has to work double..remove moisture and lower the air temp...Also depends o what speed you are driving at....the higher the faster the compressor is turning...
 
Last edited:
Is it normal for the AC system to start blowing "cool" air out of the vents pretty much immediately, but take about 5-10 more minutes before it is "ice cold"? I hooked up manifold gauges to it before, and found that the high and low side pressures were within specification.
sound like all of my cars , and more so when the humidity is high almost instant cool air and roughly 10 to 15 minutes before the heat and humidity is extracted from the cabin.
 
Think of the system as a sealed system with a fixed volume of refrigerant. The system is cooled by the compressor raising the the pressure of the refrigerant, pumping it through the orifice tube ( some have an expansion valve) where the sudden drop in pressure and resulting phase change drops the temperature of the refrigerant. The refrigerant then runs through the evaporator where it cools the ambient air going across the evaporator. The evaporator has a certain mass and the initial cold refrigerant is bringing down the temperature of the evaporator itself. Once the evaporator is good and cold it is more efficient in cooling the air. This all takes time.
 
Last edited:
I've come across a few people claiming their AC blows full cold right away, but don't have another new vehicle to compare to. My vehicle is 8 years old and I'm trying to determine if the AC is underperforming, but I just can't recall if it was like this when it was new.
 
Last edited:
I've come across a few people claiming their AC blows full cold right away, but don't have another new vehicle to compare to. My vehicle is 8 years old and I'm trying to determine if the AC is underperforming, but I just can't recall if it was like this when it was new.
You can pick up one of these and then compare your car to a friends car.

32BD61F9-0222-4AA7-8077-BCCD77B39C6B.jpg
 
I've come across a few people claiming their AC blows full cold right away, but don't have another new vehicle to compare to. My vehicle is 8 years old and I'm trying to determine if the AC is underperforming, but I just can't recall if it was like this when it was new.
No system does that. It takes a certain amount of time for the compressor to feed compressed refrigerant into the condenser and then for liquid to travel to the expansion valve, and then cool the evaporator. As noted above the ductwork can also be quite warm, so this takes a bit of time to cool down as well.

None of which is to mean that it takes more than a minute or so depending on engine RPM. At idle it will take a little bit longer.
 
Any refrigeration system takes some time to start working properly. Coils need to get to a steady temperature and expansion devices need to settle down. These items can take up to 20- 30 minutes.
Variable refrigerate flow systems take time to ramp up and blower speed to settle down.
 
Is it normal for the AC system to start blowing "cool" air out of the vents pretty much immediately, but take about 5-10 more minutes before it is "ice cold"? I hooked up manifold gauges to it before, and found that the high and low side pressures were within specification.
Somtimes mine doesn't seem to cool very well. Then I shut it off for a minute, then turn it back on and it works well. No clue why. happened more than once.
I would give the A/C condenser a good soaping and hose down.
Also make sure your cabin filter is clean.
 
So what is the consensus on the time it should take for a typical well performing automotive AC system to start blowing full cold air from the vents during 80F and 40% humidity weather while travelling above 45mph.
 
Last edited:
@explorer2030 , I recommend that you take a class at your local Community College in auto or regular HVAC.
As many have already said, there are so many variables. Interior and exterior temperatures and volume of air, are the coils clean, the type of refrigerant, the speed of the compressor , the humidity, etc, etc.
Also some new cars are moving to a more conventional refrigeration system (EVs) so comparing new vs old are two different standards.
 
The real issue here is too many variables. If parked in the sun and then you get stuck in traffic, expect to sweat. I do, and I don't even live in NV, AZ, FL, NM, TX. etc.
 
So what is the consensus on the time it should take for a typical well performing automotive AC system to start blowing full cold air from the vents during 80F and 40% humidity weather while travelling above 45mph.

I would say about one minute.

80F isn't really hot, just a bit warm and 45 mph is fast enough to get the compressor turning and keep the condenser cool.

In fact, if it's 80F and 40% humidity, just roll down the windows because that sounds beautiful.
 
If your A/C is on "recirculate", as it would be for max a/c, then as the cabin cools down, the air coming out of the vents will be getting colder. That process might take 5-10 minutes.
 
Humid air doesn’t make the AC system work twice as hard or harder at all. The efficiency may drop if the humid air causes the evaporator coil to partially freeze over, but if the system is functioning properly, that shouldn’t happen.

Moisture removal by the AC system is a by-product of its function, not its main purpose. AC system is simply removing BTUs, so it’s based on temperature difference. Both dry and humid air at the same temperature have the same amount of BTUs as far as heat energy, thus require the same energy to remove the heat.

Problem is with humans and how we perceive dry vs humid air. Humid air feels hotter and less comfortable to us then dry air at the same temperature. Therefore we feel like it takes longer to cool the cabin down, simply because we don’t feel the same comfort level. So we either lower the temperature to get that same comfort level, or wait longer for the humidity to get lower.

And since lowering moisture from the air is simply a by-product of AC function, it takes much longer then lowering the temperature.
 
Back
Top