Advantages/Disadvantages to leaving A/C on in winter

My opinion - if your inside temp is set at 75, and your NY outside temp never makes it above 70 (not accounting for solar thermal...) the only impact would be the drain from the AC indicator light switch....

Actually I would think - simply leave it on AC, and in the case you have a 55 day with bright sun in the car while parked, the AC may kick in after starting. And actually, like any vehicle it's a good thing to circulate the AC fluids and mechanics during winter downtimes.

 

The A/C compressor is only used when needed, and only at the required speed. In addition to cooling, the compressor is used to dry the air, so it will sometimes run in defogging situations. The car is fairly smart about when to use it, so any mileage hit is minimal and worth while.

Tom

 

Temperatures here have dropped to 0-10°C. My experience is that turning off the A/C compressor do create some fog on the windows (corners of the windshield and part of the side windows), especially since the system in AUTO mode keeps the fan at such a low speed (once the desired temp is reached). Turning the A/C compressor back on solve the issue.

I hence decided to leave the A/C on, although I’m not sure about the impact on fuel consumption; it should be minimal at these low outside temperatures.

 

Heh. I turn it on, my wife turns it off. Montreal - 0-10c.

My best trick - a small 500w 110vac block heater connected to an extension cord and an outdoor timer, at least 30 mins before I drive out.

Defrosts nice from within. Very useful in sub-0c conditions, or when there's freezing rain. I adjust the 30mins to 1-2 hours depending on conditions.

So I drive out without the heater to the highway...about 5-6 minutes...then turn on the heater usually to a low setting.

Installing a block heater this time around also. That should bring down my 6.0-6.5l/100km to under six in the extreme colds of jan/feb/march.

 

It's a myth to think the A/C compressor run/not run is controlled by outside temp. It's controlled by -cooling demand-. If the -interior- temp is too high re the set temp. then the compressor will run. I haven't seen a big mileage hit from running the compressor, although there a hit.

What WILL happen to lower your mileage is -heat demand-. IF the A/C system is asking for heat, AND the engine coolant temp is below a certain threshold, then the engine will run even while you are stopped. This will noticeably drop your mileage. The threshold varies and it appears the variation is caused by a temp reading I can't get on the Scangauge. For example, while warming up, the engine will be forced to run while stopped (at a light, for example) when the coolant is below about 63C (the engine will start up when it drops below that value). But after driving for a while, engine having fully warmed up, the engine will stop even when the coolant temp drops to 50C.

The easy solution is to turn off the A/C system when you come to a stop while the car is warming up. Turn it back on when the light turns green. Once warm enough (coolant above about 68C) you can leave it on.

I've found the limited sunlight we get right now can actually keep the interior warm enough to keep heat demand off even with outside temps of +5C. Oh, and I really mean "limited sunlight". I'm at 54 deg north.

 

i am guessing the biggest drawback would be running seat heaters more than normal to combat the chill.

its beltless so it uses no power when "idling"