DIY: Unlink A/C from Defroster

[jambo101]

Originally Posted by SilverGlow

Why would anyone disconnect A/C to the defroster mechanism?

There is no faster way to remove moisture from the windows and air then using an A/C. If you don't like the coolness, move the temp control to full heat.

This DIY has to be the most idiotic yet! And for what benefit? Surely not for gas savings, as the savings is insignificant....you really need to fill your time doing something useful, productive, and not devoind of logic, and utility.

I have no problem with the A/C removing moisture from the interior of the car for the first couple of minutes,but once the car is warmed up and windows are clear why do i now need the A/C on when just un A/Ced air from the vents will keep the windows clear. In fact its somewhat of an insult from Toyota to put in this feature as i'm quite capable of pushing the A/C button when i need A/C.

[dybbuk]

An insult? Don't most car manufacturer's do this automatically anyways? All the cars I've ever owned sure have. As Rick said it helps to keep the lawsuits down. Might give this a go, I think I'd unsolder it rather then break it though.

[drt1120]

Though, the knob has a few sticky points. I didn't pay enough attention before to know if I made it stickier or it has always been this way. I can't think of anything I did that would affect the smoothness of the knob.

Thanks for the info on this. I did it a few weeks ago and love not having to run the AC in the defrost mode. I also had the problem with my knob being sticky after I disabled the switch but it turns out that those gears are keyed inside and if you do not line them back up it will stick a every time that smaller gear goes around. Each gear had a notch in it and needs to be lined up to prevent the sticking.

[toast]

Couldn't you save some bother by just pulling the fuse for the a/c or pull the plug off the compressor clutch?

[dreamteam]

I agree with Toast, had the same problem with my defrost, pulled the fuse on the air.
It's clearly marked and easy to get to........liked the results so well, that I pulled the fuse on the wife's '07 corolla. Suddenly, we are both getting better mileage!
Now, this won't work so good if you live in a hot climate........, up here, I won't have to put that fuse back in until spring.

[CTScott]

Originally Posted by dreamteam

I agree with Toast, had the same problem with my defrost, pulled the fuse on the air.
It's clearly marked and easy to get to........liked the results so well, that I pulled the fuse on the wife's '07 corolla. Suddenly, we are both getting better mileage!
Now, this won't work so good if you live in a hot climate........, up here, I won't have to put that fuse back in until spring.

People often forget that the A/C is turned on automatically with various settings. Pulling the fuse definitely works as an absolute verification that it is off, but in the case of the Yaris, doing the mod mentioned above definitely turns off the automatic mode, but still lets you turn it manually (without stopping to put the fuse back in).

[Lewis]

WARNING!

I just did this today. I want to warn people who are comptemplating it to leave plenty of time and go very slowly. It is an extremely delicate proceedure and maybe I'm hamfisted but I broke one of the pull out white tabs removing the white piece to get to the curcuit board and had to spot glue it to get it together again so that it was solidly sitting in the holder. The tabs are a very very thin plastic and can snap easily.

Despite the extra bother described above I'm glad I did it because I live in a very damp wooded area and am always running the defroster/defogger. I want to have the choice of engaging the compressor and losing performance and using more gasoline or not engaging the compressor for AC based on whether I judge it's needed in the climatic conditions of the moment. There have been many times a smidgen of heat would have done the trick defogging without AC IMO.

[Lewis]

I just want to take a moment to say THANKS to Stran for doing this DYI. I have run the car two days with this mod and am very happy with the result. One of these days has been cool and drizzly and would have needed the defogger with the compressor running before the mod and now a bit of heat and fresh air on the windschield did the trick saving gas and the bother of turning on and off the defroster constantly to clear the window.

THANKS again Stran!

[yaris-info]

I spoke with the Toyota tech and he said disconnecting the A/C during winter (could be mild winter) is a bad idea. Besides quicker defogging, one of the reasons is to keep A/C compressor running at times, therefore to prolong its life and avoid premature failure.

[stran]

If it's fogging, I turn on the A/C manually to defog quicker. You can also cycle the A/C manually during winter to keep the seals from drying out.

This mod helps you defrost faster. (Frost = ice on the outside)
Also saves gas once you're done the initial defogging.

[darkMINI]

Think of it this way, if you had bought a car with no A/C, would it be any more dangerous to drive in inclement weather simply because it was lacking dryer air? Most of the cars I have owned either had no A/C or it was removed for simplicity or longevity reasons and I have never noticed a problem with defogging. Having the A\C engage automatically every time you want to defrost/defog is similar to believing idiot lights are better than gauges.

[bronsin]

Hmm what about putting in a switch to cut the power to the AC instead of pulling the fuse (or doing the mod maybe)?

The mod sounds tricky so i want to pull the fuse instead.

I doesnt need AC in winter in NJ

But not cycling ac once in a while prolly isnt good for it.

And you might want ac defrost in an emergency even in winter.

Is an ac power disconnect switch easier than the mod or visa versa?

[barryware]

when the compressor is allowed to run based on the status of the A/C switch or the position of the air selector knob, it won't run for long anyway in the winter. The compressor runs and cycles on and off based on refrigerant pressure.

When it is cold out, the compressor may start but because the refrigerant pressure will be too low based on temperature to continue to run, it will shut itself off. I really do not see the need to disable the operation based on the position of the selector knob.

If it is warm enough, you may want the compressor to run and aid in defogging the windows. If it is cold enough and heat alone will do the job, the compressor isn't going to run anyway.

[CTScott]

Originally Posted by bronsin

Hmm what about putting in a switch to cut the power to the AC instead of pulling the fuse (or doing the mod maybe)?

The mod sounds tricky so i want to pull the fuse instead.

I doesnt need AC in winter in NJ

But not cycling ac once in a while prolly isnt good for it.

And you might want ac defrost in an emergency even in winter.

Is an ac power disconnect switch easier than the mod or visa versa?

Adding a switch would be a bit less risky (the risk being breaking the little plastic tabs when taking apart the knob). The switch would simply need to interrupt the light green wire in pin 4 of the 8 pin connector on the back of the knob.

[CTScott]

Originally Posted by barryware

when the compressor is allowed to run based on the status of the A/C switch or the position of the air selector knob, it won't run for long anyway in the winter. The compressor runs and cycles on and off based on refrigerant pressure.

When it is cold out, the compressor may start but because the refrigerant pressure will be too low based on temperature to continue to run, it will shut itself off. I really do not see the need to disable the operation based on the position of the selector knob.

If it is warm enough, you may want the compressor to run and aid in defogging the windows. If it is cold enough and heat alone will do the job, the compressor isn't going to run anyway.

I find that even in below freezing temperatures that the compressor engages far more frequently than you would expect it to when running in defog mode.

[rick996]

I'm glad bronsin posted to this thread recently. I hadn't seen it before. I just did the tab removal. It took just 10 minutes. I never liked the link of the defroster to the A/C. Thank you stran for posting the original hack (3 years ago).

[A-Dingo-Ate-My-Baby]

Originally Posted by rick996

I'm glad bronsin posted to this thread recently. I hadn't seen it before. I just did the tab removal. It took just 10 minutes. I never liked the link of the defroster to the A/C. Thank you stran for posting the original hack (3 years ago).

I am not sure I understand this. My AC turns on with a button press.

2010 Yaris 5 door US spec with manual temp control knobs.

are you saying that the A/C turns on by itself in certain modes ?
my A/C light will only go on when I press the button

[rick996]

Originally Posted by A-Dingo-Ate-My-Baby

2010 Yaris 5 door US spec with manual temp control knobs.

are you saying that the A/C turns on by itself in certain modes ?
my A/C light will only go on when I press the button

Yes. Whenever you are in one of the 3 defrost modes (full or split). The light doen't come on. All modern cars that I know of do this. It makes the A/C last longer to run the A/C compressor once in a while during the winter. I will put the A/C on manually to accomplish this, but only when I am going down a long hill using DCFO.