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Discussion Starter #1
So this is something very similar to what I did with my 2002 Protege5. Our 2004 to 2009 Mazda 3's manual HVAC system is very similar.

Our vent selector is indicating the floor and windshield, or the windshield vent, the A/C system is switch on. The big butt, is that the A/C light fails to indicate.

One micro switch need to be removed from the HVAC circuit board, then bridge between two terminals. After that is completed, the A/C will only turn on when the A/C is pressed.
 

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Nice solution to this issue. And Bravo on having the fortitude to find it. This is what happened when Mazda used Ford's climate control system. The compressor also ran on full floor (heat).

Sent from my SAMSUNG-SM-G891A using Tapatalk
 

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Nice solution to this issue. And Bravo on having the fortitude to find it. This is what happened when Mazda used Ford's climate control system. The compressor also ran on full floor (heat).

Sent from my SAMSUNG-SM-G891A using Tapatalk
I like to have the A/C compressor running when using heat because it helps dry out the air in the cabin. Otherwise there can be too much humidity and the windshield doesn't defrost properly. But I prefer when I can decide to have the compressor on or not.
 

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I forgot to ask! What is the expected length of time for this job, and how big of a PITA is it to get to the A/C circuit board?

And super thanks for posting this information!
 

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Discussion Starter #5
I believe, going slow it's an 1.5 hours. I thought it was easy. As long as your soldering skills are good it can be pulled off. Be sure to zoom in on the picture showing the little bus bar I soldered, bridging to terminals where the switch was. If you miss that step, the A/C will remain on.

Humidity is not as much of a problem as
you might think. The a/c coming on automatically creates and exacerbates humidity levels in your car( shut your car off, return to it 30 min later, poof, you windows fog up instantly).

And yes, when the vent selector is indicating between 12 to 3 o'clock the a/c is automatically turned on. The above solution corrects this.
 

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Discussion Starter #6
This should also be the same for the early generation mazda 6's with the manual climate control.
As an update, I've been getting 32mpg average, to 35mpg. This is mostly city driving as I only have a 7 minute commute to work. And I am enthusiastic in my driving habits?.
 

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I like to have the A/C compressor running when using heat because it helps dry out the air in the cabin. Otherwise there can be too much humidity and the windshield doesn't defrost properly. But I prefer when I can decide to have the compressor on or not.
Great point. That is what the A/C being on does. If it doesn't then the issue is probably that the fresh/recirc switch is on recirc instead of fresh. That will always fog a windshield in defrost mode. Most vehicles will not allow recirc in defrost mode because of this. Our one Camry does allow it and I have to explain to my daughters about the difference between using it in the hot summer verses not using recirc in the cold winter on defrost. They come home from college and the switch is on recirc and you can see where they have been wiping the inside of the window because of fogging up. "Oh, that's why" they respond. Got to love kids.
 

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Discussion Starter #8
Yes and no. You have 4 causes/sources of excessive humid situations, let me explain.
*Weather, the place you live.

*rain, you and your clothing get saturated

*a water leak inside the vehicle from Rain or washing the car. My mazda 3 was leaking water through cracked body seam sealer in the upper gutter area near the top of the hatch opening.

*** and the 4th, I give this lots of stars due to a main cause the a/c system being on with out having ample driving time to be shut off before turning the car off.

If you have ever had the chance to see your ac evaporator when your a/c system is operating, you will notice that it is iced up with a healthy coating of ice. Now when you leave your car, this ice melts. Now you get a small amount that drains out from the air box, there will still be thawed water droplets covering the evaporator. Now you get back to your car, turn the climate control system on, the air blows against the windshield, then you notice your window fogging up, you turn the a/c on, after a short bit, the fog goes away.
Now you have just started this cycle once more.

Now, there is a way to control this agitating and time consuming, fuel wasting problem.
After having a job that I had to drive my car to more than 30 sites in an 8 hour period( rainy days were the worst). This uncontrollable problem had to get sorted, some times it would be bad enough that I'd have to wait with the car idling in the parking lot for over 5 minutes, on a busy day I just couldn't tolerate it. Nore did I want to have no choice of consuming more fuel.
Try it, you can always go back. It's easy.
 

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I spoke to the dealer about the AC compressor coming on - If you put the vent selector in upper and lower selection, the compressor is not suppose to come on.

Protege 5. same thing
 
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