Proper A/C Operation


Tom and Ray: You gave some bad advice on a recent show regarding operation of a Subaru air conditioner in “max” or “recirculate” mode. (This is not surprising given the average July temperature in Cambridge is about 53F, so I don’t expect you to be A/C experts.)

Here is the proper way to start up and operate your A/C in hot weather. This will yield both optimal A/C system performance, and best fuel economy.

1. Start your vehicle, open the rear windows, and turn your A/C to “normal” with the fan on high for a couple of minutes. You will be using hot outside to force the even-hotter inside air out of your vehicle.

2. Turn your A/C to “max” or “recirculate”, fan still on high, for a few minutes only (typically 5 minutes or less even in the hottest weather) to chill the interior of the vehicle and A/C system components.

3. Turn your A/C back to “normal” and adjust fan as necessary.

4. Enjoy.


Also, don’t forget to put your windows back up before Step 2.


In this particular episode it seemed to me that Tom and Ray completely missed the caller’s point. She didn’t say anything about recirculate. She said she had the vents closed. That suggests to me that the individual registers on the dash were in the closed position and might have prevented any air from circulating through the climate control system at all. This might have explained her problem too.


Very excellent auditory observation ! I agree.


From our perspective in Phoenix, we are uniquely aware of how hot it gets inside a glass box (passenger compartment) when a car is parked in the sun. My Infiniti starts off with the “fresh/recirc” on “fresh” by default whenever the car is started. This lets “cooler” air from outside the car (alot cooler than the air inside the car!) into the mix when the A/C is turned on. Another poster suggested opening a window to let the hot air out…I usually open the sun roof a crack to let the hottest air out the top. I hope this sheds light on the Subaru owner’s question. Uncle S