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Discussion Starter #1
I'd like to be able to run the windshield defogger without running the A/C. From the factory of couse when you set the knob to defog it automatically turns on the A/C. Any mods I can make to shut this "feature" off?
 

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See the last post on this page:
http://www.mazda3forums.com/index.php?topic=53106.1230

However, when I tried to get the control unit out, there wasn't enough slack to unhook the wires without completely dismantling the dashboard. So I gave up.

Note that the A/C also runs unbidden with the selector on "Floor" or "Floor + Defrost."

Lodge a complaint with Mazda. If enough owners bitch, maybe they'll issue a TSB.
 

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Why would you like to run in defrost/defog mode without the A/C? Without the A/C running the vehicle will not defog properly. The reason they don't give you the option of turning it off is that they end up getting more complaints for not properly defogging when people have to remember to turn the A/C on. The A/C will not run unless the ambient temperature is above a certain temperature. It varies a little, but usually around 40°F or so. I'm not sure about Mazda, but usually the A/C compressor will only come on when you are in a mode that puts air to your windshield. This would be mainly defrost and Floor defrost on a manual system. The ATC will turn the A/C on when ever it need to do so. Anyway just a couple of thoughts.
 

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Discussion Starter #5
I didn't know it wouldn't turn on below a certain temp. That cool. But there are a lot of other times I'd just as soon run without the compressor. My wife's car doesn't have AC and her windshield defrosts just fine as did my last car where I ahd disabled this "feature." I just don;t need the car thinking for me.
 

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[quote author=bmohr1 link=topic=67114.msg1155966#msg1155966 date=1169140125]
Why would you like to run in defrost/defog mode without the A/C?[/quote]

Because it's hardly ever necessary. Half the cars I've ever owned didn't have A/C at all, and this one is the first that doesn't let me decide when to use it. Somehow I managed to survive. I must lead a charmed life...or maybe it's because my IQ is well into double digits.

A/C is handy to defog the windshield quickly, but once it's clear a little heat will usually keep it that way, without costing 3 or 4 mpg. I can't think of any sane reason to force the compressor on when the selector is on Floor. And I can't think of any reason to run the compressor without illuminating the LED on the A/C button. It's MY car, Mazda--stop "helping" me drive it.
 

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If you really want a heater only system you could unplug the compressor's electrical connector so the clutch would never engage. That would make it like your old cars.

The reason they don't turn the light on the A/C button on when the clutch engages is that the light would flicker. The compressor will cycle on and off depending on the load required. if the light was only on when the compressor was engaged it would drive you nuts. I've actually seen tests where they test the defog of a vehicle with and without the compressor and the difference is amazing. I really don't mind that they run it anyway. If the load on the evaporator is not that high it won't stay on for long and you won't really notice it.
 

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The main reason it uses the AC for defog is the dryer/evaporator. It pulls the humidity out of the air, and blows dry air.
 

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[quote author=lanny link=topic=67114.msg1153979#msg1153979 date=1169046880]
See the last post on this page:
http://www.mazda3forums.com/index.php?topic=53106.1230

However, when I tried to get the control unit out, there wasn't enough slack to unhook the wires without completely dismantling the dashboard. So I gave up.

Note that the A/C also runs unbidden with the selector on "Floor" or "Floor + Defrost."

Lodge a complaint with Mazda. If enough owners bitch, maybe they'll issue a TSB.
[/quote]

you can/must (with some difficulty), detach the other end of the wires. They are clamped on with a phillips head screw under the dash on either side footwell. You don't detach them from the control unit. It is a pain on the driver's side. I used a very stubby craftsman phillips with the knurled metal knob, a total of about 1.5" to get them loose.
-billm
 
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