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Main Forums => The Roundtable => Topic started by: Perd Hapley on July 10, 2017, 09:29:56 PM

Title: A/C and the large automobile
Post by: Perd Hapley on July 10, 2017, 09:29:56 PM
In a giant crossover/SUV/van, with separate front and rear climate controls, do I need to run both, when no one's back there?

My new(er) vehicle is a large crossover type of thing. It allows me to run AC front and back, or just in the front. I figured I wouldn't use it, when there's no one back there. But then, if I'm only running the front, isn't it conditioning all of the air in the cabin, anyhow? So I've taken to running front and rear when it's been sitting out in the heat for a while, and then cutting off the rear AC once we're underway, and things are cooled down. But when things get into the 90s, or above, having both of them feels a lot better.

When there are passengers in the rear seats, it's a no-brainer, but should I expect to have to run both front and rear most of the time?

The owner's manual is no help, so ???


Title: Re: A/C and the large automobile
Post by: grampster on July 10, 2017, 11:30:46 PM
Trade it in for a Pinto. :old:
Title: Re: A/C and the large automobile
Post by: dogmush on July 11, 2017, 02:12:00 AM
Are you comfortable in the front seats with just the front AC on?  Then only run the front.  Are the front seats still a little warm?  Then run the rear as well to remove more heat.

The AC systems are designed to run independently, and at their "max" setting indefinitely.  So it's really a matter of your comfort.
Title: Re: A/C and the large automobile
Post by: Fly320s on July 11, 2017, 08:48:42 AM
I think there is only one AC system for the entire car.  The rear AC is just a vent off the main line, which helps spread the air around better.

When you run the AC in your house, does each room get cooled or do you prefer to have the rooms at different temps?
Title: Re:
Post by: lupinus on July 11, 2017, 08:50:41 AM
If anything the rear vents maybe have a separate fan. Run it how ya like it

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Title: Re: A/C and the large automobile
Post by: K Frame on July 11, 2017, 08:53:32 AM
"I think there is only one AC system for the entire car.  The rear AC is just a vent off the main line, which helps spread the air around better."

It depends, actually.

Some vehicles have a vent from the main evaporator.

Some vehicles have a single compressor with multiple independent evaporators, like a multi-unit mini split system.

And some vehicles have completely separate A/C systems. Those are normally the larger passenger vans, like the Strider airport van. Castle Key has one of those (ugly damned things) set up for dogs, and it has the standard dash A/C system and a separate compressor/evaporator that's mounted on the roof.
Title: Re: A/C and the large automobile
Post by: Perd Hapley on July 11, 2017, 09:13:36 AM
If it helps, mine is a 2010 Traverse.
Title: Re: A/C and the large automobile
Post by: dogmush on July 11, 2017, 09:26:41 AM
If it helps, mine is a 2010 Traverse.

A quick Google shows parts available for refrigerant lines and an evaporator/blower module in the rear.  It's likely you have two evaporators running off of one compressor and condenser.  I've seen dual condenser designs, but only on military and commercial vehicles.

Either way it's no big deal to run the rear system.  Probably a *little* more drag on the engine for moving more refrigerant, but not a lot.
Title: Re: A/C and the large automobile
Post by: bedlamite on July 11, 2017, 09:50:02 AM
Do your part to help global warming, turn on both at max and open the windows.
Title: Re: A/C and the large automobile
Post by: K Frame on July 11, 2017, 09:51:56 AM
"It's likely you have two evaporators running off of one compressor and condenser."

That's exactly how the Traverse works. That's what I described as a multi evaporator/single compressor min-split system.

As noted by others, it really all comes down to a question of comfort for you and your passengers. If you're comfortable running only the front A/C, go with that. If you're more comfortable running both front and rear, go with that.

The system has more than enough cooling/circulating capacity to cover both units running full blast.
Title: Re: A/C and the large automobile
Post by: T.O.M. on July 11, 2017, 09:57:36 AM
Wife drives a 2016 Ford Flex, with the dual climate system.  In the summer if I"m driving her car and alone, I'll run the back until the interior cools down, then shut it down and run only the front.
Title: Re: A/C and the large automobile
Post by: 230RN on July 11, 2017, 09:58:18 AM
My little Subie station wagon with a whole lot of glass has a hard time cooling off the whole car.  It's OK in the front seats with it going full blast, but I wish it had a dual system.  I gotta watch my travel time if the back is full of frozen groceries or other perishables.

On the other hand, my pickup truck with its small cabin would freeze my ass off in short order if I didn't watch it.  "Who spilled all the LN2 in here?"

Title: Re: A/C and the large automobile
Post by: K Frame on July 11, 2017, 10:07:21 AM
Yeah, I've had the same complaint about my Outback and my Forester.

Generally the A/C works well, but with just a front A/C it takes forever to cool the car down.

In the summer I use insulated bags for my perishables.