Running your A/C on Max all the time?

[nighthawk87]

Does it hurt to just leave your AC on max all the time and only adjust the fan speed to regulate cooling? I seem to remember one telling me that leaving recirculate on for too long can cause microbial growth in the AC system.

Also, is there any harm or additional wear on the system when in Max?

Lastly, does anyone know if the fan speed or temperature of running the AC has any increase or decrease effect on MPG? I thought the effect was either it was on or not. I know folks that will run their fan on low to avoid hurting MPGs. I tell them it doesn’t matter what speed it’s at and it only matters if it’s on or off.

Thoughts?


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[yoda]

The only difference between max AC and regular AC is the recirc door position, Max AC draws air from inside the cab, regular AC draws air from outside.

Running on MAX all the time will not hurt anything or cause more wear.

The microbial growth would probably depend on outside vs inside humidity levels, personally I don't really think it matters.

As far as mpg I suppose having the blower speed on a lower setting may cause the compressor to run a little less. Compressor on time is usually based on evaporator temperature, less airflow would = evaporator colder= less compressor on time, temperature setting would have no effect.

In reality I don't think mileage difference would be measureable

 

[Firebird]

Here in Florida, it's on max all the time

 

[TRCM]

What's this max setting you mention....mine is set to 72 deg.....................


I suppose in a regular system, running it on max all the time (recirc'd air) could assist with microbial growth, especially if you always have a lot of people in it. The recirc won't remove the moisture & germs from everyone's breath, and it could build up over time (germs mainly). Using fresh air would help flush things out.

Just like your house, go all winter with the windows shut and germs/etc build up & the house gets a 'smell' to it......then come spring, you open the windows and air it out....same basic principle.

 

[naumaa1]

I don't remember what the source was, but I heard that you want to run fresh air without the a/c on through the system for a little bit before shutting down to get rid of the excess moisture. Personally I just run my system on auto and let the system do its thing

 

[Neil E]

If it is really hot in the truck, I set it on the coldest setting not in Max (recirculate), and once it cools off a little bit, I set it max or recirculate. I also crack the windows or open all the way to get the hot air out before setting it to max.

 

[Random_Walk]

I love in Oregon... What's A/C?

Kidding. It shouldn't hurt, except for the odors you may build up...

 

[Tach_tech]

Depending on trim levels. Some trucks will have a humidity sensor mounted by the rear view mirror. If the humidity reaches a calibrated level the recirc door will automatically be opened to allow fresh air into the cab.

So if your truck has the AUTO function for your hvac you can leave it on max/recirc all you want and it’ll take care of it.

Also an old dirty cabin air filter will create some bad smells as well.

 

[Flip-er]

What naumaa1 said.
You can tell if someone is always running there a/c by the rank smell sometimes in a cab.
I personally cut my a/c off a few minutes before getting where I am going to remove the moisture out of the ducts.
JUST something I have always done.
My wife on other hand doesn't and has a mold like smell sometimes in her car.

 

[Marine Les]

The manual says not to use recirculate all the time and to run fresh air with max blower speed to dry the system before shutting it down. I've read this advice before and think it is good advice.