Crank It or Leave It? We Tested Auto Climate Control to Find Out

Somewhere between the correct way to hang toilet paper and the right quantity of decorative pillows on the bedspread comes another spousal debate: how to use automatic climate control. Do you pick a temperature, set the automatic mode and let the system do the rest? Or do you ride herd on the settings, adjusting everything throughout the drive?

Related: Song of Ice and Tire: Does Snow Buildup Cool Car Performance?

Cars.com is a house divided in this regard, mirroring our recent survey in which almost 60 percent of respondents who have automatic climate control said they ignore the auto setting. The two camps on our staff became known as the nerds, who trust that the automotive engineers behind the automatic settings have their backs, and the philistines, the kind of unsophisticated people who turn their house thermostat up to 90 degrees thinking it will heat up faster and probably reject science in general. (If it isn’t obvious, the authors and all of the editors who conducted this test are nerds who thought they knew how the test would go.)

We put the dueling theories to the test. On an early March morning, the two sides drew swords — OK, calibrated digital thermometers — and had at it.

Nerds and Philistines, Start Your Engines!

We parked two 2018 Volkswagen Atlas SUVs equipped with Climatronic automatic climate control overnight. Both began the test with cold V-6 engines and cabins measuring 48 degrees. The designated nerd and philistine each started his engine simultaneously.

In Atlas 1, the nerd set the automatic climate control to 72 degrees on full-auto mode and kicked back.

In Atlas 2, the philistine also set the climate to 72 degrees but selected the lowest fan speed, aimed at his feet, waiting for the engine to warm up.

Here’s how it went:

A few minutes into the test, the nerd’s approach had pulled ahead. The automatic setting balanced fan speed and heat while it waited for the engine to warm. At the five-minute mark, Atlas 1 had tacked on 3.3 degrees; Atlas 2 had added less than 1 degree. The nerds envisioned a smug victory speech.

Their elation was short-lived. In Atlas 2, the philistine observed some heat emanating from a vent after the five-minute mark, cranked the fan to full speed and activated the dashboard vents along with the floor ones. Despite having practically the same amount of engine heat at its disposal, the automatic mode in Atlas 1 restricted fan speed for minutes on end — and it didn’t take many minutes for Atlas 2 to move ahead.

Seriously, it flew. By the seven-minute mark, Atlas 2 approached 60 degrees. Atlas 1 registered just 53.4 degrees. The chasm only widened from there. On full-blast, Atlas 2 hit 72 degrees within just 15 minutes; Atlas 1 still hovered around 60 degrees. (For the record, if the SUVs were being driven, the test would have gone faster, but keeping them at idle, close together with no other variables like speed or wind, makes the comparison more accurate.)

Once Atlas 2 reached the target temp, the philistine hit the automatic setting and celebrated. (Actually a nerd playing the part of a philistine, he didn’t celebrate at all but quietly pondered how he would hide these results from his philistine spouse.)

In Atlas 1, the fully automatic setting didn’t hurry to bring the heat. It eventually lumbered past 72 degrees, crossing the mark some 30 minutes in — long after the philistine had declared victory. Cue the memories of playground tetherball, because the nerds got smoked.

So What Happened?

Our interpretation is that the automatic mode simply didn’t ramp up the fan to the high setting, or even close to it. By cranking the fan to high, the philistine simply got more hot air into the cabin faster. This happened even though the automatic setting in Atlas 1 recognized sooner that engine heat was available and started blowing a little harder. Once the philistine took action, his setting got the job done faster. It was a clean win in this case — or in this car, as it were.

Cars aren’t like home heating and air conditioning. Many home furnaces or air-conditioning systems have one constant blower speed and produce one level of heating or cooling; it reaches the thermostat’s setting based only on how long it runs. (Don’t bother trying to convince a philistine.) Cars, however, have two ways of adjusting the temperature — by varying the blower speed and by mixing hot and cold air.

Though they share these abilities, cars are as different as the people who drive them. We’re confident that another model with different automatic ventilation programming would have resulted in performance closer to the manual approach. In fact, some cars allow the driver to tweak the automatic programming, pre-selecting how fast the blower can blow. A blower running at high speed can be intrusively noisy or drafty, and some people don’t like it (as some of the respondents to our survey suggested). Preventing such negative reactions is one objective of the engineers behind automatic modes, and it’s probably responsible for the Atlas’ conservative fan speed and Atlas 1’s loss in this test.

Whatever the reason, the philistines have a point. Our test illustrated how the automatic setting can be comparatively worthless if the speed of temperature change is your priority. In defense of the nerd approach, however, performance is only as good as the philistine monkeying with the settings. Forget to crank the fan until well into the engine’s warmup, and it could take the cabin considerably longer to heat up. Go anything less than full blast, and the warmup could also take longer. Set it too high in a bid for faster heat, and you could end up too hot and need to go back at it again.

How About Cranking the Temp Setting?

Does cranking the temperature — in effect overshooting what you eventually hope to reach — induce faster warmup? Our testing indicates that, unlike conventional home heating systems, it definitely can (at least in small increments) thanks to variable fan speed:

• With temperatures stabilized in both Atlases, we put both in the fully automatic mode and observed how long it would take to raise cabin temperature 3 degrees by goosing the temperature setting 3 degrees in one car and 6 degrees in the other.
• Within four minutes, our 6-degree crank had increased temperature by more than 3 degrees. The 3-degree crank, by contrast, had raised temperatures just 1.6 degrees.

Predictably, cranking up the temp in automatic mode ramps up fan speed more than a modest temperature increase does — and fan speed, as we observed in the first test, affects cabin temperature in a big way. Play with your own car, and you’ll probably notice the blower speed increases as you set more extreme temps, either incrementally or dramatically when you put it on the high or low end of the range.

Conclusions

One conclusion that shouldn’t go unmentioned is that the automatic setting in the Atlas, for all the heat it’s taken — or, in this case, failed to dispense — prevails on one basic count: You don’t have to futz with it as much. Pick the temperature, hit the automatic setting and it modulates everything accordingly … eventually. Another conclusion is that sometimes the philistines win — because, sometimes, even philistines are right.

Cars.com’s Editorial department is your source for automotive news and reviews. In line with Cars.com’s long-standing ethics policy, editors and reviewers don’t accept gifts or free trips from automakers. The Editorial department is independent of Cars.com’s advertising, sales and sponsored content departments.