How-To: Disabling Automatic A/C - Defrost modes

ZapWizard

Electro-modder
Disabling automatic A/C - Defrost

2003 Mazda Protege







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Most modern cars are getting more and more fool-proof.

One thing that car makers now use is "Automatic A/C and Defrost"
What this does, is if you turn the knob on your car to defrost, then the car pulls in fresh air, and turns on the A/C automatically.
Taking in fresh air, and de-humidifying it, the windows defrost faster; but it is not always needed or even wanted.





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When using the defrost vent modes, you can't use recycled air.
And your A/C is also turned on, robbing horsepower.
(Even though the A/C light does not turn on)




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Once completed this modification allows you to take back that control, you set the fresh air, and A/C settings no matter what vents you use.



<HR>The tools needed are:

  • Philips screwdriver
  • Small flathead screwdriver.
  • Needle nose, or similar pliers
  • Exacto-knife


<HR>Thanks to MaxxMazda for the original help. http://www.protegeclub.com/forum/showthread.php?threadid=25430





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First remove the glove box.
Open it, push in the sides at the top, gently lower it, the pull towards the driver side, and down to release.





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Look inside and towards the drivers seat.




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Locate the temperature control cable and disconnect it.

Gently push the tab in and pull the cable off the white control arm.

The push down on the black metal holder, and pull the cable surround out.



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Next move the drivers side, and locate the vent control cable.



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Repeat the same steps to disconnect the vent control cable.





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Next you need to pull the center panel out.

This is done by pushing the vents down, and pulling with both hands.




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With the center panel hanging out, disconnect the hazard signal button,
and the two connectors at the rear of the A/C control assembly.



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You can now remove the entire center panel.

Be careful to note how the control cables come out, so that you can put back in the correct way.

Once removed unscrew the A/C control assembly from the front panel.



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With the panel removed, carefully pull the three control knobs off.



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/Edit- removing the A/C and Defrost buttons is not needed



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You should now have no knobs on the front



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Pull the front faceplate off by pulling up on the two holding tabs on each side.

You will see a circuit board behind the faceplate, don't pull on it.

We don't need it. But you could make changes to the LEDs or the colored caps on the backlights here.



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We need to get under the other black plastic cover.

But first you need to remove the temperature control cable.

Do this by spreading the center tabs on the white holder, while pulling on the black cable surround.

If have found this step easiest by spreading the tabs with needle nose pliers.

Do not try to pry the cable out, or pull up in any way!





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Once the black surround is out you can tilt the cable up, and out of the control arm.



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You can then unscrew the circuit cover and remove it.

There are two push tabs towards the front holding it in place.




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Thanks to TZH for these larger images.


With this circuit board exposed you can see one of the micro-switches at the right.

The other is on the other side of the circuit board.

You do not need to remove these switches, but simply cut their connections.

On the circuit board you will see two thin traces near the white holder.

One has only a short connection on this side of the circuit board,

the other you can see traveling to one of the micro-switches.

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Using an exacto-knife cut into the circuit board, and through the traces.

This is only a two-sided circuit board, so you can cut pretty deep, as long as you don't cut through to the other side.

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It is best to make two cuts through the traces, about 1mm apart from each other, then use the exacto-knife to remove the copper between the two cuts.

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This will disconnect the micro-switches from the rest of the circuit, and disable the automatic A/C and defrost.

If you want to restore this functionality, you can solder a jumper wire between the solder points of each trace to restore their function.





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Once the cuts are made you are finished, and can start to put things back together in a reverse order.

Again make sure to route the control cables carefully so they do not get snagged or loose.

You can now have full control over your A/C, Defrost and Vents.

Remember, when you actually do need to defrost your windows, turn on the A/C and take in fresh air.
 

Poseur

stop honking I'm surfing
Contributor
:
03.5 Lsr Blue P5
Very well-written, thankyou. I've always thought it was kinda cool that they idiot-proofed it all for ppl, but ultimately being a control freak gets the best of you. and not everyone need the world padded for them.
 
Very nice write-up,and pics. How long did this Mod took? I want to do this so bad.But i'm afraid i will mess things up. was it easy??
 

ZapWizard

Electro-modder
It took about 30 minutes.

The hardest part is removing the black plastic surrounds from the holder, and re-routing the stiff cables when putting things back together.

The only part that you could break something easily, is removing the A/C and Defrost button caps. If you do break the plastic tabs, I guess you could glue the caps back on somehow.
(Simple hot glue would allow for easy removal again later)

I actualy did the removal twice today while working on a moonroof always on mod, that I will post later tommorow.

I will do it again when I change out the LEDs, as I want a 100% deep red dash.

I tried to photograph every step, so it should just be a matter of following the guide.
 

thumpr

"since yesterday"
that's very cool - my sweetie likes to have her feet warm without air blowing on her face - the automatic a/c makes that impractical - is it possible that one of the traces to cut is about the floor vents, and one about the windshield vents? nothing is ever that simple right.
 
I DID IT!!!!!(headbang) I can't believe it myself! and i didn't break anything too.Thanks zap for your wonderful guide. it was a piece a cake!! Thanks a lot!!!!!!!!!!
 

Matthew

Original Member
Contributor
:
2016 MX-5 Club, Ceramic
you make the best how-tos i have ever seen, congrats on another nice one.
 
:
2003 Sunlight Silver P5
Great write-up and reminds me of how much I miss the HVAC in my old E30 BMW.. 3 sliders, one each to operate the defrost vents, dash vents, and floor vents respectively. You could have all three on if you wanted. Then a knob for fan speed, a button for AC, and a button to recirculate the air. Ahhhh total control of the system.
 

1Canuck2

Registered Moron
I have a Canadian P5, I swear I can have my window vents on with no AC, but that's going by long lost memories of summer. I'll test this tomorrow.
 
I have a Canadian P5 and AC turns on automatically with defrost.. same as the US models..

Great write up.. I did this mod last year and have loved it.. I find it incredibly insulting that Mazda trusts me to DRIVE the car, but not handle the "complexities" of their vent system..

Saved lots on gas.. and eliminated all the "fog" problems I was having.. do it! :)
 

tzh

:
Mazda Protege 5
Some pictures

I did it last weekend, the process is pretty easy. Thanks ZapWizard.
Here I have couple of detail pictures.
This is what you will see after opened the black cover. There are the 2 traces.


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They are flat copper lines.


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Make sure you get rid off all the copper between the gap.

 

ZapWizard

Electro-modder
Thanks for those excelent images tzh.

Do you mind if I download, host, and integrate them into the guide?
(With thanks to you of course)
 
X

xfimpg

fraay said:
I have a Canadian P5 and AC turns on automatically with defrost.. same as the US models..

Great write up.. I did this mod last year and have loved it.. I find it incredibly insulting that Mazda trusts me to DRIVE the car, but not handle the "complexities" of their vent system..

Saved lots on gas.. and eliminated all the "fog" problems I was having.. do it! :)
Hey Fraay

How much did you calculate or estimate that you saved on gas?

Mike
 
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xfimpg

Thanks to everyone who contributed to this solution!
I just finished mine and am looking forward to the results.

Mike
 

chuyler1

goes to eleven
Moderator
:
2013 CX-9
Sorry to ressurect this but I wanted this done from the day I got my P5. I like to run the heat through the defrost-floor in the winter time because it keeps the dry air from blowing in my face (and making my eyes dry out). However, I also like to get good gas milage which won't happen if I'm running the A/C all winter long.

Excellent post! This should be sticky if it isn't already.
 

eting_pro5

Thread Killer
:
'03 Pro5
Woah woah woah....mega serious question.

The ventilation system is always moving air through it, even when it's off. Additionally, although the blower is turned to 0, the temperature dial still has a noticable effect on the air coming out.

Does this mean if I leave the controls on defrost and the blower to 0, is my AC still on??? If so, I think Mazda owes me a few grand in gas money....I've never gotten good gas mileage, but I always drive with the vent control on defrost.
 
eting_pro5 said:
Woah woah woah....mega serious question.

The ventilation system is always moving air through it, even when it's off. Additionally, although the blower is turned to 0, the temperature dial still has a noticable effect on the air coming out.

Does this mean if I leave the controls on defrost and the blower to 0, is my AC still on??? If so, I think Mazda owes me a few grand in gas money....I've never gotten good gas mileage, but I always drive with the vent control on defrost.
No your A/C is not on when the switch is at 0.

The temp dial makes a difference because it's hooked up to a manual "door" that alows engine cooland to either come into the heater core or not. The air flowing in from outside always passes over the heater core. when you turn the dial to hot, hot coolant runs into the heater core, the outside air passes over the hot core and voila hot air with setting still at 0.
 
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