Historically Toyota tells part time 4x4 owners to do this in the manual or the overhead tag on the sun blocker (drive it once a month/certain distance). I don't have this issue as I have full-time 4WD with all of my SUVs.

 

Every time you have defrost turned on, it activates the AC compressor to dehumidify the air. Works much like a heat pump in a central HVAC system.

 

It is not. Every major manufacturer of residential AC units, and nearly all installers, specifically recommend to NEVER run your AC unit unless the outdoor temperature has been above 60 degrees for at least 3 days. Most modern units actually have a low ambient control circuit to prevent the unit from starting if it is too cold outside, to prevent damage to the unit. The oil in the compressor thickens significantly at colder temperatures, increasing strain on the unit and reducing lubrication at the same time.

https://kaiserac.com/running-air-con...0the%20process.
https://homeairconditioner.ca/blog/c...in-the-winter/

I have commercial AC units for my server room at work, which HAVE to run when it's cold out. Those have heaters built into the condenser units to keep the oil and refrigerant temps within the unit's operating range. But even with that, the outdoor units fail and need service/repairs WAY more often in the winter than they do in the summer. I'd say over the past 12 years, at least 85% of our non-scheduled maintenance has been during the December-February window. When one of the three finally failed catastrophically (repair estimate: $12,350), guess when that was? During a cold snap in late November, when the temperature dropped into the 30s. This was not a coincidence.

A car's AC system is completely different. It's in the engine bay (usually physically attached to the block), which heats quickly. So while it's fine to run those in the winter (and most automatic climate systems do so), it's very bad advise to suggest people do the same with their home AC.

 

Correct.....and one also needs to remember that home A/C is not always traditional A/C, but sometimes electric heatr-pumps, which operate on a different (and more efficient) principle....I have a heat pump in my own house. Small heat-pumps are also sometimes used in BEV and hybrid vehicles for climate-control. They also operate on different principles than traditional auto A/C....and the advice I gave in the OP doesn't necessarily apply to them.

 

i believe most cars equipped so if left in "auto" will always run the A/C compressor even if you have the heater on full. so for folks that run on "auto" year round, you are already doing what the OP suggested. good reminder!

 

For my Toyota 4R. I can turn it off so it does not engage in AUTO. But my 04 I can’t

 

I thought this sentence in the manual implied AC doesn’t function in low ambient conditions.

“■ When the outside temperature is low
The dehumidification function may not operate even when “A/C” is selected”

Don’t most comfort AC systems have low ambient lockout controls as opposed to process cooling systems ie food freezers, etc. that have low ambient compensation? Can’t imagine a car AC compressor running in temps below 55° F. Isn’t the AC switch just an enable switch, enabling the AC system make decision on many factors, including low ambient?

 

at home, too? whaaaat? it'll be freezing in the house if i use the a/c in the middle of winter.

 

At home, it you have a heat pump, the compressor will run summer or winter, unless it is so cold outside that the compressor can't efficiently extract any heat, in which case the regular electric-furnace heaing-coils run, using more energy at a higher cost. A regular electric A/C unit, of course operates differently from a heat pump....there, the compressor only runs in summer..

 

It'd be great if some ppl could even turn the defrost on to begin with, instead of fogging all the windows up....Kinda similar driving w/o the headlights on & running the drl's at nite & early in the morning.

 

my home central a/c compressor seized up because we hardly ever used it.

 

In older cars, the recirculate-function of the climate control could be activated when the windshield defrost was on. That was as bad or worse as no defrost at all, because it recirculates the same moisture around inside the car and on the windows. The fresh-air-intake should always be on with the defrost...and, in many newer vehicles, it is automatic, and will not allow the recirc-mode in defrost.

 

I use auto mode for HVAC on all of my cars, with AC enabled and I have no doubt that the compressor is not running all of the time. It turns off and on as needed. So I believe you are correct.

 

I wouldn't buy a new vehicle that was designed/configured for the fresh-air-intake to always be on with defrost. My wife and I are sensitive to diesel fumes and fumes from gas burning cars that are putting out excessive fumes for any number of reasons. The issue would be particularly problematic when we start our vehicle on a cold morning, turn on the defrost, back up, and then have to breath the cold engine exhaust. The only time we switch to fresh air is when we are close to home and want to dry-out the HVAC system prior to parking, to prevent long-term, moldy/musty odors.

 

I let a friend test-drive my GLI last night, and I cringed when the first thing he did was turn the A/C compressor off. Decided to leave it alone though. I agree, I see no downside to leaving it on, or at the very least, taking advantage of the "Auto" climate mode. Let the computer decide, eh?