When to turn on car AC?

[javacontour]

I'm surprised no one has given this answer yet.

Turn it on when it's hot, or you want to remove moisture from the passenger compartment.

What about vehicles with automatic climate control? The computer decides when to turn up the heat or AC depending on what it wants. Our Sienna wouldn't crank up the fans for heat until the coolant was warm. I suspect it did similar for the AC, but I don't recall the specifics.

 

[scurvy]

Originally Posted By: FirstNissan
I heard this from my neighbor, he's an old know-it-all who doles out free advice all day, some of it good, most of it wrong. Anyways, he comes over to tell me that its not good to start the AC on the car immediately after starting the car, he said its better to turn on the AC after a few minutes, after the car has warmed up. Any truth to this?


Yes. It's true, this advice is wrong.

All cars have load management built into the start algorithms, you needn't worry about it. Turn it on whenever you need cooler or less humid air and tell your old know-it-all neighbor to poop in his hat the next time he doles out a gem like that one.

Plenty of cars these days have reciprocating variable-displacement compressors (mine do) and change the load required based on the cooling demand. I see a much bigger fuel economy drop on my Scangauge when running the fan at higher speeds due to this.

And yes, AC is often necessary in cool weather to help remove humidity from the passenger compartment. That's what fogs up your windows - I often run the heat & AC at the same time to dry out the passenger compartment in spring/autumn. On mk4 VWs, the AC won't come on under about 5ºC but at that point there's usually low relative humidity after it's been warmed in the heater core.

 

[rcy]

Originally Posted By: scurvy


On mk4 VWs, the AC won't come on under about 5ºC but at that point there's usually low relative humidity after it's been warmed in the heater core.


Many (if not all) cars have a low temperature lock out to prevent damage to the compressor (I don't know the mechanics of why low temperature operation can damage the compressor).

 

[scurvy]

Originally Posted By: rcy
Many (if not all) cars have a low temperature lock out to prevent damage to the compressor (I don't know the mechanics of why low temperature operation can damage the compressor).


It's to prevent evaporator icing.

 

[ARB1977]

Unless your a Jetta its best to turn on the AC after the car starts. Ours would smoke alittle behind the steering wheel at startup with the AC on.

 

[lexus114]

Originally Posted By: ARB1977
Unless your a Jetta its best to turn on the AC after the car starts. Ours would smoke alittle behind the steering wheel at startup with the AC on.



I`m sorry, but what??

 

[CaspianM]

I don't need to turn my ac asap if inside. Outside I role the windows down for 1 minute if hot and then AC.
AC comp is not a huge load but if it taxes you a few miles then it is a load of some magnitude. I like to warm up the car easy as like avoiding getting into interstates til is warmed up or not drop into D right after cold start up. Nothing would be hurt otherwise but I feel it is better way if you don't mind the delay in sequential start up.

As someone said I turn off the ac and run high fan before parking the car inside letting the evaporator to empty itself so it won't pee in my garage and to prevent mold formation.

 

[KrisZ]

I usually don't pay attention whether the AC is on or off when I start the car, however most of the time I turn the AC off a minute or two before I arrive at my destination. The reason for that is to dry up the evaporator and prevent mold growth.

So far I think this method works, as after 5 years my AC doesn’t have mildew smell.

 

[scurvy]

Originally Posted By: ARB1977
Ours would smoke alittle behind the steering wheel at startup with the AC on.


I'll second lexus114's comment: WHAT?!

Originally Posted By: CaspianM
...I turn off the ac and run high fan before parking the car inside letting the evaporator to empty itself so it won't pee in my garage and to prevent mold formation.


Originally Posted By: KrisZ
...most of the time I turn the AC off a minute or two before I arrive at my destination. The reason for that is to dry up the evaporator and prevent mold growth...


As well, I turn off the recirculation several miles before I get home and the AC a few blocks away to help dry off the evaporator. Mk4 VWs are notorious for the mildewy AC smell, doing this keeps it from happening as does making sure the evaporator vent in the firewall is clear.

 

[ffhdriver]

You've lost me, how does turning off the AC prevent the drain from plugging?

 

[scurvy]

It doesn't. Making sure the drain is clear is a separate step to keep the AC fresh & clean.

Many mk4s left the factory with the heat shielding on the firewall incompletely punched out for the evaporator drain. So you have to take the 7 seconds to stick a finger in there and make sure the drain opening is punched out completely so it can drain. That and turning off the recirculation helps keep the evaporator from smelling funky.