Yesterday, I covered the history of single-zone automatic climate control systems. Today, I’d like to talk about something a little more modern: Dual-zone (and multi-zone) climate control.
Dual-zone climate control (the ability for the driver and passenger to set their own temperature) is a feature that I sometimes call the “Marriage Saver.” I generally like things cooler than Mrs. H. does, and a dual-zone system allows us to both be comfortable at the same time. While it seems like multi-zone climate control has always been around (most of my cars since the early 2000s have been so equipped), it is easy to forget that this technology first appeared in the late 1980s.
As I covered in my previous installment, the first car with fully automatic climate control was the 1964 Cadillac. Lincoln got automatic climate control in 1966, and Chrysler in 1968. But these were all single zone systems. It would be several more decades before a manufacturer took the seemingly obvious leap to give passengers their own separate temperature controls.
1988 BMW 750iL Climate Control
While the US automakers were the early innovators with ATC, the Germans were the first movers for dual-zone. Based on my research, the first car with dual-zone automatic climate control was the 1986 BMW E32 7-Series. The E32 was not launched into the US until the 1988 model year and Google let me down trying to find a picture of this unit, so we will have to content ourselves with a picture from a 1988 US model (above). Note that it allows the driver and passenger to configure different airflow directions and even separately enable and disable automatic mode, something I don’t think I’ve ever seen on a modern system.
1991 600SEL Dual Zone Climate Control. The REST button allows the system to continue to operate after the engine has been turned off.
The 1991 Mercedes Benz W140 S-Class was a technological tour de force when it came out, including such then-novel features as double-paned glass, rear popup parking markers (remember those?), and power folding mirrors. It was the first car with a dual-zone automatic climate control with digital control. The switchgear is typical Mercedes Benz of the era, with obtuse labels, big rotary dials, and chunky buttons. Like the Bimmer, each side of the car could have airflow directed in different directions.
600SEL Rear Climate Control
Interestingly enough, the W140 600SEL was also the first car with a four-zone climate control system, with separate temperature settings for the left and right rear passengers. While other cars have had separate front and rear A/C (for example, the Mercedes 600 “Grosser” and certain ’60s and ’70s Chryslers that I will cover in an upcoming Cold Comfort post), this I believe is the first to allow separate temperature controls for the left and right rear passengers. The rear HVAC system was truly a separate system, with its own heater core and evaporator, meaning it was theoretically possible to run the A/C in the back, but not in the front (and vice versa).
1991 Buick Dual ComforTemp system (passenger control on left)
Honorable mention goes to the 1991 Buick Dual ComforTemp system, available in the Regal and Park Avenue. The reason for the honorable mention is that while the passenger did get a temperature control, they did not have a digital temperature display, nor was their temperature setting fully independent of that of the driver. Rather, the passenger just had a red or blue indicator showing their temperature relative to that of the driver (warmer or colder). This system did offer one innovation that the BMW and Mercedes did not have – the ability to enable and disable the dual-zone functionality.
Dual ComforTemp is actually a clever cheat, as it still (mostly) a single zone ATC. This system still only had a single interior thermostat and single temperature display, so all the passenger control did was adjust the blend door on the passenger side to mix in a little extra warm (or cool) air relative to what the driver was getting. If the driver turned their temperature up or down, then the passenger went up or down as well, plus or minus their specified offset to the driver’s temperature. But still, this was more passenger side temperature control than pretty much anyone else (other than Mercedes and BMW) was offering in 1991.
As near as I can tell, this semi-dual climate control system remained exclusive to Buick exclusive for many years. Oldsmobile and Pontiac never used it, and Cadillac wouldn’t get it until 1996. (Edit: it appears that this system was used on the Aurora, which I must confess I kind of forgot was an Oldsmobile)
Lexus added separate driver and passenger temperature to the LS400 in 1995. This system pretty much fits the template of all modern dual-zone setups: Individual temperature control for the passenger and driver, but the air direction (floor, vent, defrost) and fan speed are the same for both sides, along with the ability to enable and disable dual-zone operation. So while the Mercedes, BMW, and Buick systems are interesting historical oddities, I consider this to be the true granddaddy of all modern dual-zone systems. Unlike the previous early dual-zone systems, the operation of the Lexus system is at once obvious and intuitive. No wonder its design has been copied by virtually every other automaker.
1996 Cadillac Seville STS
Cadillac introduced its first dual-zone climate control system in the 1996 Seville and Eldorado. As previously mentioned, this system was just another version of the semi-independent Buick Dual ComforTemp system. Note that the number in the right-hand display in the picture above was the outside temperature, not the passenger temperature, as it was not a true independent system. The Seville and Eldorado would eventually get true independent dual-zone climate control in 1998.
2003 Lincoln Town Car Dual Zone Automatic A/C
While Lincoln was an early adopter of single-zone ATC in 1966, they were very late to the dual-zone party. The 2000 LS was the first Lincoln to be so equipped. The Town Car wouldn’t get dual-zone A/C until 2003.
Today, virtually every manufacturer offers some form of dual-zone climate control (and many now offer three- or four-zone climate control systems on minivans and SUVs).
As a kid of the 80s I appreciate the proliferation of vents for people not in the first row regardless of the amount of control over the temp.
As the owner of a mid-trim Buick (Preferred instead of Essence) I’m irritated that you have to buy a top trim model now to get the dual zone function. For a few years there Buick made the dual zone feature pretty much standard. I’ve seen lots of low trim cloth seat Lesabres from the late 90s with the passenger slider.
The LeSabre got the same Dual ComforTemp as the Park Avenue /shown in the photos starting in 1992 as an option, though it was part of a package then too IIRC.
My mother’s 1998 LeSabre Limited had it. IIRC (and I might not) the control was situated on the passenger door under the sail window.
I think Buick may have split the Essence trims, as my Encore is an Essence but in the middle-price range for the model, and has dual-zone control but no digital readout, just knobs.
Buick’s trim groups are confusing but at least they don’t put a goofy badge on the back. I could care less if it’s the Essence or the Chesapeake or the Sparkle Motion, at least it had the options I wanted and nothing I didn’t.
I like dual zone controls, it makes my passenger happy to control their side. No more “it’s too cold” “it’s too hot” arguments.
I think the European BMW E32 climate control system looked exactly like the US-spec version you’ve pictured. The picture below is from a 1987 German E32 brochure — looks the same.
However, I checked a 1986 Car & Driver review of the E32… that article had a (small) picture of the dashboard, and the controls looked different, with big rotary dials in place of the dials shown in these pictures. I’m not sure if that was a pre-production model, or maybe their test vehicle didn’t have the auto. climate controls (though ACC was mentioned in the text).
Overall, I agree with your assessment that dual-zone climate control is a marriage saver!
My dad had a ’95 Park Avenue with the Dual ComforTemp feature; even if it wasn’t a “true” dual zone system, it worked very well. You could dial in plus or minus 5 degrees F from the main setting, enough to account for varied individual preferences in most cases. The rear seat got it’s own vents too, no temperature control but you could vary the airflow or turn it off. The system was very good at selecting the appropriate ducts and fan speed, and keeping the selected temperatures. And the control on the passenger’s door looked mad cool with its red and blue lines indicating temp variation.
The other car I recall from the early ’90s with an odd dual climate control system was the top of the line Saab 9000 sedan for one year only, 1992 if I recall correctly, that had some sort of dual air conditioner setup. There was a huge doghouse in the trunk that held the rear A/C, taking up about 1/4 of the luggage space and relegating what remained to an odd L shaped space. What I don’t know is if this was for the rear passengers or the front passenger, and whether it meant it would cool down faster than single A/C equipped cars. I never saw the interior setup of a dual A/C car in person and can’t find one online either.
If there was ever a Dad stereotype mine fit to an extreme its obsessive thermostat management, mr 68°. The first vehicle with dual zone we had was the Villager minivan, with rear compartment controls up on the roof near the passenger sliding door. We took many family trips to Colorado and Florida in that thing, and was I comfortable in back? Oh noooo. First of all they removed the middle row seat since my Mom was an interior designer and could haul large items easily, and the family consisted of me and the dog so it was no practicality loss on trips, on those the dog bed was in its in place, while I lounged in the rear row like a limousine (which was pretty awesome), but that meant I was well out of reach of my climate controls. My Dad would actually reach all the way back from the driver seat to make sure the rear vents were matching the blistering cold setting he had set for the front, lest he feel a warm draft from behind. I outright closed the rear vents but their design never fully blocked flow so I’d end up freezing back there until we hit a rest stop and could bask in the summer heat. I never made an issue of it to be fair, but in hindsight as an adult it kinda has me steaming.
His Lexus was the first car I experienced with the dual zone in the front compartment with digital readouts for the exact temperature, and the very first time I cranked my side from 68° to 75° he was borderline irate “if you wanted it warmer why didn’t you say so, why do I even have A/C on if you’re going to set it so high!”. I was in my teen years at that point and snarkily snapped back “It’s dual zone, control freak, I didn’t change your side!”. And that was that, up to that point he didn’t realize that was a thing in luxury cars
Is it just me or is that 1996 Cadillac climate display misleading on purpose? There’s no way I would have thought the rightmost temperature was outside until I read it in the article then noticed the small legend to the right. I would have thought it was actual dual-zone climate control.
I thought the same thing when I first saw it. Classic 90’s GM…
The Volvo 850 had dual-zone climate control whether you got the automatic system or not. Heck, the 850 could be had without A/C in some regions…and still had dual-zone heat controls!
Some generations of GM pickup, Chrysler minivans, and the GM W-Body could also be equipped with non-automatic dual zones.
The non-automatic dual-zone HVAC system is an interesting hybrid. I thought about including it in this post, but ran out of room. Maybe I’ll cover it in a future post.
Tom, excellent article. It’s very fascinating. I would like to throw my vote in for finding out more about the GM “hybrid” climate system that went into the trucks and some cars. My 2003 Suburban and current 2005 Impala have that system. If you look at the Impala’s dash (it’s a base model mind you), it has the two sliders, with one side having a “D” and the other having a “P”. Interesting system, I’ve never given it much thought until now.
Tom, thank you for writing this. I had non-automatic dual-zone HVAC in a 2005 Rally Edition Pontiac Aztek. Best system ever, no joke. When using heat with the air direction set to the panel/floor setting with the temp slider less than halfway to Hot you could get very warm air to the floor and much cooler air through the panel vents. If you ever had cold feet this system was wonderful. I don’t know how many GM cars had a similar system. But I’ve missed it ever since. Do you know what the name for this system was?
My 99 Chry T&C had a manual dual-zone system that worked very nicely. Fan speed was shared, but each side got its own temp selector control. I guess it was actually 3 zone because there were rear controls too. That is one of the many cool features about that minivan that I miss.
Oldsmobile did pick up Buick’s dual zone gimmick, at least by the mid 90’s. My ex father in law had a ’95 Aurora with a passenger zone. It was controlled by a knob mounted on the door panel.
I wouldn’t be surprised if the original Aurora were the only Olds with dual zone HVAC because it had been planned as a Cadillac and reassigned to Olds.
Came here to say this. Both generations of the Auroras had the dual zone climate. I’ve had three of them (1999, my current 2001 and a 2003) and they all have had the temperature knob on the passenger door.
My 1995 & ’96 Olds 98s had the knob on the passenger armrest as well.
My ’04 LeSabre has the two buttons on the door to adjust the passenger side temp.
I can’t find a photo online, but I’m sure the HVAC controls in my wife’s old ’84 Corona (RT140 series) had two separate sliders for driver and passenger heat. AC was just a separate blue button, so was probably a totally separate function. I would guess this was like the Buick system in piggybacking off the temp the driver chose. I didn’t care enough about the car to read up the manual and see what it was all about. Anyone else know anything about this?
Hmmmm didn’t certain year imperials have rear A/C as an option? Not exactly dual zone but close
I’ve been kinda armchair hunting for an early 1970s Mercedes SLC or SL. I can’t be sure but it seems as if the earlier euro-spec (maybe just the pre-’74 SL) models had dual zone temperature control. They defintely have a different dial setup from the post-’74 models. A real MB nerd will know more about this but to me, it’s always made the euro models that much more appealing (besides the great headlamps).
I’ve lost count of the number of times I’ve had the following conversation with my boyfriend.
Him: Why is it so hot/cold in here?
Me: because that’s what you set your temperature to last time you rode in my car.
Whats the big deal? My 64′ Ford had four zone climate control. Each window had its own handle…
My Citroen has dual zone it has quirks if you switch the engine off like to get a coffee on restart the passenger side left resets itself to the drivers side setting heat is delivered at too hot not medium but overall it works ok the compressor runs all the time according to its green light not sure if thats right or not but it works thats the main thing.
My ’92 325i (e36) had dual zone and I thought it was stupid in a car with a smaller cabin than a Civic.