Cold Comfort: The History of Dual-Zone Automatic Climate Control

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.

1998 BMW 750iL Climate Control

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

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

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

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

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

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).