This is a minor annoyance I have with all new cars. Manufacturers seem to think we're too dumb to know to turn on the A/C when the defrost (defogger) is on to speed things up. On my last vehicle (an 04 Impreza) I was able to pull the dash apart and simply snip a wire that went to a switch tripped by the **** when turned to defrost. Amazingly I was able to remember to turn on the A/C in the winter when needed to clear the window. Go figure.

Now I've noticed that on my M3 Touring HB that the AC and def will come on when the temp is set all the way down (that part doesn't bother me much)... as well as the A/C turning on when the defrost is on (although the light isn't on I can feel the engine take a hit in hp).

Does anyone know of a way to turn off or stop the A/C idiot feature from turning on with the defrost?

 

click the AC button when its on so it turns off

 

When the dial is set to defrost... the A/C does NOT light up... but the A/C is running. I assume you have a Mazda 3. Go try it.

 

Kuth, you are right, if you crank the temp dial all the way down to coldest, the AC does come on automatically.

You are also correct thatthe ACautomatically comes on when you use the defrost - I share your viewpoint that this is stupid. What I don't know is if there is a temperature cutoff (as there is on some Fords and I believe some GM products) where the AC does NOT automatically come on if the ambient temp is many degrees below freezing - which would be sensible given that if it is very, very cold, it does not enhance the defrost function one bit to have the AC running. I've read the manual thoroughly, I cannot see any notation on this subject.

A tactic I use to minimize the need to use defrost (and thus AC usage) is to crack the front passenger doorwindow, and the rear driver side doorwindow, about an inch each. Seems to createenough airflow to, in mostconditions, prevent thewindshield fromfogging without the need to have the defrost on, but not so much air flow that the cabin feels overly drafty.

A quirk of the Mazda3 is if you direct the air 100% to your feet, the AC also automatically comes on. Talk about ridiculous.

The "Keep the AC off" settings are between 7 and 11 oclock on the dial.

 

Thanks for the reply. This is probably the one thing about my new car I don't care for. Yeah, I'm picky. Other than that everything about it rocks. I had my choices down to an 08 Impreza Wagon or an 08 Mazda 3 (my previous 04 Impreza was put to rest by an elderly gentleman in a buick, R.I.P. my lil sideways snow drifter). The Mazda 3 simply killed the new Impreza on everything except the awd.

So getting back to the A/C thing, I was hoping someone had taken the time to pull their dash apart and find what wire or sensor needed to be operated on to turn that off. The last car was a quick snip of one wire. I'm guessing this one will be a bit more complicated.