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Is Katie's husband right to keep the AC off when stuck in traffic?

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Dear Tom and Ray:



My husband and I recently purchased a new car. My husband refuses to run the air conditioning in heavy stop-and-go traffic or if we are sitting in the parked car. When I ask him what the reason is, he says that since the compressor for the air conditioning is belt-driven, if there is no airflow into the engine, the car will overheat. So I'm wondering why I see everyone else sitting in their nice, cool cars with the windows up, but their cars aren't overheating. He has been this way with all of his vehicles. We have a vacation coming up with a 12-hour drive. I'm worried about long, HOT construction delays. Is he right -- should I continue to silently melt in 90-degree weather? Or can we turn on the darn AC? -- Katie

RAY: Katie, we feel for you. We really do. The reason you see everyone else sitting in their nice, cool cars is because they're not married to your stubborn husband.

TOM: He's being overly cautious. Far too cautious. For at least three decades now, all cars have come equipped with electric cooling fans. When the car isn't moving and there's no wind being pushed through the front grille, an electric fan now comes on, independent of the engine, and makes its own breeze for the radiator.

RAY: That's why cars can sit in traffic, even with the AC on, on very hot days, and still not overheat.

TOM: In fact, most cars have a second cooling fan, or a higher speed for the cooling fan, that kicks in automatically whenever the air conditioner is turned on, just to provide extra cooling under hot conditions.

RAY: Now, there is a limit to a cooling fan's effectiveness. It never will provide as much cooling air as you would get when driving 65 mph on the highway. So if you're stuck in traffic for a long time, and it's 120 degrees out, an engine still can overheat. But those are highly unusual conditions.

TOM: So the bottom line is that you're suffering needlessly, Katie. Here's what you should do: Suggest that your husband try leaving the AC on during your upcoming vacation.

RAY: Right. Just leave it on, whether you're stopped or moving. As long as the "HOT" warning light on the dashboard doesn't come on, that means the car is fine. And unless you're in bumper-to-bumper traffic in Phoenix during a horrendous heat wave, or the cooling system malfunctions, that light's never going to come on.

TOM: But just in case, wear Egyptian cotton, Katie. Good luck.

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