Quote:
Originally Posted by gascort
Coyote X is correct; the same fan is running, but with an interior intake open. This makes it more noisy and also blows harder since there's less resistance on the fan. I bet the blower motor uses the same amount of electricity on fresh or recirculating settings.
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I was wondering about the blower energy usage between normal/max. On many vehicles the outside air intake is in the cowl area at the base of the windshield where there is an aerodynamic high pressure at highway speeds that might "assist" the air flow into the cabin. On Max or recirculate you're drawing air from cabin pressure and accelerating it back into cabin pressure.
OTOH most blowers are squirrel-cage fans that are very efficient at operating with suction on the intake, and on normal mode the blower is actually attempting to pressurize the cabin (unless it's very leaky or has a designed pressure relief) by cramming outside air inside. My truck has a pressure relief system on the rear cab wall that blows air out in front of the bed on normal mode so my blower doesn't blow harder on MAX it's just noisier.
I was interested to see this article since I have had my own thoughts on the subject, but come to find out everything you recommend I already do. I go one step further and actually turn off my compressor when I'm in MAX at low blower setting and have reached a comfortably cold temperature. My truck allows me to have the compressor on or off in any given setting but if someone's vehicle doesn't they could tap a switch in series with the refrigerant pressure switch circuit (the switch that detects the high-limit pressure between the condenser and the expansion valve that shuts off the compressor until the pressure drops) to manually turn off the compressor without being able to force it on. Which brings up one more point: if you want to be cool but not cold, do not turn up the temperature dial as it merely blends hot air into the conditioned air. Cycle the A/C on/off to make it warmer than the low-blower MAX A/C would normally make it to minimize compressor operation.
Additional point: When starting your car after it has sat in the sun lower the windows with the A/C on normal mode to pull the interior temp down. Outside air is cooler than cabin air at this point so normal is more efficient, plus it pushes the superheated cabin air out the windows. This might only take a minute or less before you feel cold air at the vents, at which point you can switch to MAX and roll the windows up.