Quote:
Originally Posted by AsleepAltima
probably none of those reasons. almost every single newer car out there (and lots of old ones) will have the compressor come on when you turn on defrost. the reason i gave is exactly the reason why. just because air is heated, doesnt make it dry air. ever lived in a hot and humid place? same thing only its everywhere and not just in your car...
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Well, when air is heated the relative humidity in that air drops. So if you look at a typical winter in the northern midwest (I live in the Chicago area), it's probably a bit below freezing and above 50% humidity. If I heat that air up to 70 degrees (F) then the relative humidity is way below 50%. Plus it warms up the windshield glass, reducing the amount of interior moisture which will be condensed onto that glass. By contrast, the A/C core will be struggling to reduce the temperature and humidity of the incoming air by any significant amount. And while the compressor is on, it's taking power from the engine and reducing my gas mileage.
Now, you could make a case that running the A/C now and then during the winter will help prevent problems with the system - the owner's manual recommends doing just that. But I don't see the need to run it every day by default.
Hey, has anybody ponied up the ~$210 for the service manual yet?