[MrB]

Hi,

I saw there were people wondering how to disable the A/C in defrost mode in a Toyota Matrix.
This mod is a bit of a pain in the butt, but really simple.
In the '06 Matrix the air vent control has a little cam on the back of it that throws a miniswitch when the knob is rotated right to either of the defrost modes.
It's behind the heater control assembly, so you have to remove the big trim facia around the radio and a/c, recirc, defrost switches. If you grab it on the bottom and give a slow steady firm pull it pops out, you then flip it upward to disengage the top clips and it just comes free of the dash. (I love how simple Toyotas are to work on) Pop out all the wiring harness plugs to the switches and clock and it's free of the dash. Be careful not to scratch the finish.
Next, you remove the radio by unscrewing the four screws that attach the radio's mounting frame from the dash. There will be a white nylon standoff mount that guides a wire harness around the back of the radio clipped onto the frame next to the upper left mounting screw. You can squeeze the mount clips with a pair of needle nose pliers and it pops free of the frame. Pull the power and speaker plugs and antenna and the radio's out.
Now you can get behind the heater controls.
Grab a flashlight and a dental mirror or other small mirror. Turn the vent control knob all the way to the left and look with the mirror and flashlight behind the heater control assembly at the right side of the vent control. You'll see the switch and a little white nylon mini plug with two black wires leading to it. If you have a tail, now would be a good time to whip it out and use it to hold either the flashlight or mirror, otherwise you're going to need three hands for this next step.
Hold the flashlight in your mouth or with your tail to bounce the light off the mirror - which you're holding with one hand - and onto the switch. so you can see it. You now need to take one finger of your free hand, reach way back in there and with your fingernail - and manual dexterity you never realized you had until now - pry that little plug open.
That's it, you're done except for putting everything back together. You don't need to do anything else with the plug. It will just hang there close to the switch and won't interfere with the vent control as it rotates.
That's all there is to it. It takes care of the pesky a/c defrost issue and it's a non-destructive mod. Everything else works exactly as it did before, the a/c doesn't come on when you switch to defrost. You can still manually switch it on and off with the switch on the dash when you want to clear your windshield quickly. If you're ever so inclined you can just slip the back on with some needle nose pliers and everything's back to original spec.
Sorry no photos. I just did the mod this afternoon and didn't think about posting this for you guys till after I was done. Once you know where to find that switch, the whole job takes maybe 20 minutes. I had to hunt for it to find it, so it took me a little longer.
Enjoy the fuel savings,
MrB