Disabling automatic A/C - Defrost
2003 Mazda Protege
2003 Mazda Protege
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.
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)
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
<HR>Thanks to MaxxMazda for the original help. http://www.protegeclub.com/forum/showthread.php?threadid=25430
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.
Look inside and towards the drivers seat.
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.
Next move the drivers side, and locate the vent control cable.
Repeat the same steps to disconnect the vent control cable.
Next you need to pull the center panel out.
This is done by pushing the vents down, and pulling with both hands.
With the center panel hanging out, disconnect the hazard signal button,
and the two connectors at the rear of the A/C control assembly.
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.
With the panel removed, carefully pull the three control knobs off.
/Edit- removing the A/C and Defrost buttons is not needed
You should now have no knobs on the front
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.
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!
Once the black surround is out you can tilt the cable up, and out of the control arm.
You can then unscrew the circuit cover and remove it.
There are two push tabs towards the front holding it in place.
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.
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.
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.
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.
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.