Help Needed: Unlink A/C to Defroster

[stran]

I don't like the way how the A/C has to be on when I turn on the front defrosters. I think there are two ways to fix this: fake out the detector switch so the car doesn't know you turned on the defroster, or kill the circuitry that automatically turns on the A/C.

In case you don't have the Factory Repair Manual Handy:
http://www.etimago.com/yaris/repairmanual/EWD.pdf
http://www.etimago.com/yaris/repairmanual/Air%20Conditioning.pdf

This might get a little technical:
Option 1
One guest is that the switch could be inside the control knob itself, and the signal could be turned off by shorting the signal wire or soldering in a resistor. Take a look at page 245 of the Air Conditioning manual for more info about this. Or there could be a switch in the air damper that controls flow to the front defroster. See page 10.

Option 2
The Electrical Wiring Diagram Manual (filename: EWD.pdf) on page 239, 240, and 330 mentions "Defroster Mode Detection SW" in the context of air conditioning. SW means switch. The problem is that I don't know where this switch is physically located in the car. The diagram on page 50 and 52 might help answer this question but I can't put the two together.

Any help is appreciated, and I know I'm not the only person who wants to get rid of this.

[TheRealEnth]

i really dont mind?

[IllusionX]

there IS a switch inside the knob that activates the compressor AND THE BUILT IN HEATER...

you do not really want to get beyond that that in messing around the wires...

[auxmike]

What about in the deep of winter, will the A/C still kick on?

[CTScott]

I don't like the way how the A/C has to be on when I turn on the front defrosters. I think there are two ways to fix this: fake out the detector switch so the car doesn't know you turned on the defroster, or kill the circuitry that automatically turns on the A/C.

In case you don't have the Factory Repair Manual Handy:
http://www.etimago.com/yaris/repairmanual/EWD.pdf
http://www.etimago.com/yaris/repairmanual/Air%20Conditioning.pdf

This might get a little technical:
Option 1
One guest is that the switch could be inside the control knob itself, and the signal could be turned off by shorting the signal wire or soldering in a resistor. Take a look at page 245 of the Air Conditioning manual for more info about this. Or there could be a switch in the air damper that controls flow to the front defroster. See page 10.

Option 2
The Electrical Wiring Diagram Manual (filename: EWD.pdf) on page 239, 240, and 330 mentions "Defroster Mode Detection SW" in the context of air conditioning. SW means switch. The problem is that I don't know where this switch is physically located in the car. The diagram on page 50 and 52 might help answer this question but I can't put the two together.

Any help is appreciated, and I know I'm not the only person who wants to get rid of this.


I looked at the EWD. To disable it you would need to cut a trace on the printed circuit board for the AC switch assembly. I would have to pull one apart to figure out which trace, but the other option is to replace the switch. The EWD indicates that there is one "w/ Defroster Mode Detection SW" and one "w/o Defroster Mode Detection SW".

[Revsson]

I don't like the way how the A/C has to be on when I turn on the front defrosters. I think there are two ways to fix this: fake out the detector switch so the car doesn't know you turned on the defroster, or kill the circuitry that automatically turns on the A/C.

In case you don't have the Factory Repair Manual Handy:
http://www.etimago.com/yaris/repairmanual/EWD.pdf
http://www.etimago.com/yaris/repairmanual/Air%20Conditioning.pdf

This might get a little technical:
Option 1
One guest is that the switch could be inside the control knob itself, and the signal could be turned off by shorting the signal wire or soldering in a resistor. Take a look at page 245 of the Air Conditioning manual for more info about this. Or there could be a switch in the air damper that controls flow to the front defroster. See page 10.

Option 2
The Electrical Wiring Diagram Manual (filename: EWD.pdf) on page 239, 240, and 330 mentions "Defroster Mode Detection SW" in the context of air conditioning. SW means switch. The problem is that I don't know where this switch is physically located in the car. The diagram on page 50 and 52 might help answer this question but I can't put the two together.

Any help is appreciated, and I know I'm not the only person who wants to get rid of this.

It doesn't say it in your profile, but I assume that since you joined in 2007,
that you drive an '07 LB? :iono:
Just trying to clarify if there can possibly be any difference in the model
years for the A/C.

[jambo101]

I don't like the way how the A/C has to be on when I turn on the front defrosters. .

I dont like it either,seems like a waste of energy,all previous cars i've owned never had air and i never had a defrost problem, but what is needed to defeat this operation looks like more trouble than its worth so i'll just crank up the heat a little more to overcome the permanent air when in the defrost mode:iono:

[floydisrock]

The ac compressor in a vehicle should be run to prevent clutch and bearing problems.
Every Car I've owned mentions running the ac at least once a month.
I'm guessing they just let the compressor run,so they don't have so ,many warranted a/c compressors to replace.
I wouldn't worry about the few cents your going to save disconnecting the unit,I would worry about replacing a $1000 a/c compressor.

[jambo101]

My winter setting is the defrost/floor position for the entire winter so i guess i have no other option than to have the air running all winter whether i like it or not.:iono:

[eTiMaGo]

winter or not, I believe the main reason for the AC kicking in is to dry out the air to help with the defrosting/defogging itself?

[IllusionX]

My winter setting is the defrost/floor position for the entire winter so i guess i have no other option than to have the air running all winter whether i like it or not.:iono:


you don't NEED to run with defrost/floor all winter long... put it back to the floor only when the front window is defogged.

[jambo101]

you don't NEED to run with defrost/floor all winter long... put it back to the floor only when the front window is defogged.
Tried that and the windows start fogging up again,seems some airflow is constantly needed on the window to keep it fog free' but just warm air will do the job once the car is at operating temperature,at that point the air is no longer needed but there is no way to turn it off and still have airflow over the window.:iono:

[stran]

It doesn't say it in your profile, but I assume that since you joined in 2007,
that you drive an '07 LB? :iono:
Just trying to clarify if there can possibly be any difference in the model
years for the A/C.

I have a '07 hatchback.

PS How do I subscribe to a thread if I forget to do it when I post?

[stran]

there IS a switch inside the knob that activates the compressor AND THE BUILT IN HEATER...

you do not really want to get beyond that that in messing around the wires...

Except the connection to the heater is probably via a mechanical linkage. I know that the vent knob operates via a mechanical linkage. With the car off and there's no power, you can still switch between the vents. On luxury cars I've driven before, the soft buttons activate a little motor that open and closes the damper that only works when the car is on.

[stran]

Tried that and the windows start fogging up again,seems some airflow is constantly needed on the window to keep it fog free' but just warm air will do the job once the car is at operating temperature,at that point the air is no longer needed but there is no way to turn it off and still have airflow over the window.:iono:

agreed. i also like having warm air diffused instead of concentrated at my face or feet, and the best way to do that is through the defroster vents.

[CTScott]

I have a '07 hatchback.

PS How do I subscribe to a thread if I forget to do it when I post?

07 and 08 use the same ribbed knob switches and 09 has knurled knobs. I looked at the EPC, but can't figure out from the wording, which switch is the one which doesn't automatically turn on the AC when in defogger mode.

Go to User CP (control panel) and click on list subscriptions, then you can select the notification method for threads that you have posted in.

[CTScott]

Except the connection to the heater is probably via a mechanical linkage. I know that the vent knob operates via a mechanical linkage. With the car off and there's no power, you can still switch between the vents. On luxury cars I've driven before, the soft buttons activate a little motor that open and closes the damper that only works when the car is on.

The knob that changes where the air is blowing does so by cable as you mention. Here are some pictures of what the back of the switch assembly looks like:

http://img101.imageshack.us/img101/750/pict1573gp7.jpg

http://img146.imageshack.us/img146/5665/pict1575bc7.jpg

From this thread about changing the bulbs:
http://www.yarisworld.com/forums/showthread.php?t=9857&highlight=led+dash

If you look at the close-up picture above the outer knob turns a plastic gear. I would bet that there is a boss on the gear that bumps a switch that parallels the AC switch. If so, you could just clip the boss...

[jambo101]

Seeing as you have it all apart anyway can you give us a pic of the cam/boss that activates the air while in defrost mode? dont know why Toyota couldnt have given me the option of defrost with air on or off,like its only a matter of pushing a button if i want the air on.

[CTScott]

Seeing as you have it all apart anyway can you give us a pic of the cam/boss that activates the air while in defrost mode? dont know why Toyota couldnt have given me the option of defrost with air on or off,like its only a matter of pushing a button if i want the air on.

I haven't actually pulled mine apart. I just remembered seeing the picture of it pulled apart on that thread. Based on the EWD's I think that the "option" is based on whether or not you have the "cold weather package".

[stran]

I haven't actually pulled mine apart. I just remembered seeing the picture of it pulled apart on that thread. Based on the EWD's I think that the "option" is based on whether or not you have the "cold weather package".

I'm in Cali and the cold weather package wasn't an option for me but my defroster is still linked. And thanks for showing me how to subscribe. I can follow the conversation now.

[IllusionX]

Tried that and the windows start fogging up again,seems some airflow is constantly needed on the window to keep it fog free' but just warm air will do the job once the car is at operating temperature,at that point the air is no longer needed but there is no way to turn it off and still have airflow over the window.:iono:

I don't know about yours, but both, the echo i've had and the yaris i have now constantly have a good amount of air coming out of the defrost area when it is set to foot only. If your car does fog up even when fully warm up without activating the front defrost, chances you are running with recirculated air all the time.

Except the connection to the heater is probably via a mechanical linkage. I know that the vent knob operates via a mechanical linkage. With the car off and there's no power, you can still switch between the vents. On luxury cars I've driven before, the soft buttons activate a little motor that open and closes the damper that only works when the car is on.

the connection to the heater is activated by a mechanial linkage that activates a switch. it COULD be the same switch as the AC switch when on defrost mode. My echo only had one switch there.. so...
i don't know if this helps.

http://www.postimage.org/gxJ2Ehr.jpg (http://www.postimage.org/image.php?v=gxJ2Ehr)


By the way, even in Cali, your front window fogs up, especially during rainy days. when setting your vent to front defrost, the AC actually helps in defogging your windows.

[stran]

My first DIY post.

Total Time:
7 mins (if you know what you're doing)
20 mins (if first time opening the dash)
2 hours (if you're have two left hands or missing your opposable thumbs)

Tools:
Small flathead screwdriver to disconnect wire harness and push in the little clips that holds the plastic pieces together. (But not required. I could have done it with my keys or just my fingers.)

Follow instructions for changing the LED to access the back of the vent dial. Everything comes apart really easy. On the back of the circuit board (the one with the A/C button), there is a momentary switch (momentary means it requires continuous pressure to be closed) with a little metal arm. I know this description is vague, and I'm sorry I don't have pictures, but there's nothing else on the back and once you're there, it'll be obvious. Bend the metal arm a few times and it breaks right off. Presto! No more annoying A/C with defrost. Reassemble.

How it works: the back plastic piece has a ridge that engages when the vent knob is in the defroster mode. The ridge presses on the metal arm to trigger the momentary switch. No metal arm means the ridge can't trigger the A/C switch.

For the belt and suspender people to check you have the right switch (which is what I did), you can turn on the car and press the switch and see if the A/C turns on. It's easiest to tell when the car is fully warmed up since the difference in idle speed between A/C off and A/C on is very noticeable. I also had a scangauge to check fuel flow, but you can open the hood and check the condenser fan.

Tips:

Leave the vent dial knob all the way to one side (like face vent) so when you reassemble, you don't have to worry about aligning the indicator.
There's a little bit of grease on the knob to lubricate the gears. Having some paper towels is handy.


Man, this mod made my week. I've been pissed at my defroster for so long. 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.

[CTScott]

My first DIY post.

Total Time:
7 mins (if you know what you're doing)
20 mins (if first time opening the dash)
2 hours (if you're have two left hands or missing your opposable thumbs)

Tools:
Small flathead screwdriver to disconnect wire harness and push in the little clips that holds the plastic pieces together. (But not required. I could have done it with my keys or just my fingers.)

Follow instructions for changing the LED to access the back of the vent dial. Everything comes apart really easy. On the back of the circuit board (the one with the A/C button), there is a momentary switch (momentary means it requires continuous pressure to be closed) with a little metal arm. I know this description is vague, and I'm sorry I don't have pictures, but there's nothing else on the back and once you're there, it'll be obvious. Bend the metal arm a few times and it breaks right off. Presto! No more annoying A/C with defrost. Reassemble.

How it works: the back plastic piece has a ridge that engages when the vent knob is in the defroster mode. The ridge presses on the metal arm to trigger the momentary switch. No metal arm means the ridge can't trigger the A/C switch.

For the belt and suspender people to check you have the right switch (which is what I did), you can turn on the car and press the switch and see if the A/C turns on. It's easiest to tell when the car is fully warmed up since the difference in idle speed between A/C off and A/C on is very noticeable. I also had a scangauge to check fuel flow, but you can open the hood and check the condenser fan.

Tips:

Leave the vent dial knob all the way to one side (like face vent) so when you reassemble, you don't have to worry about aligning the indicator.
There's a little bit of grease on the knob to lubricate the gears. Having some paper towels is handy.


Man, this mod made my week. I've been pissed at my defroster for so long. 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.


Excellent!!!

[auxmike]

:needpics:

[stran]

sorry dude. i don't have a digi cam. it'll be obvious once you get there.

[billk]

well my solution for the A/C not running when using the defroster took me 1 sec to fix. In fact It was all frosted over this morning and my defroster cleared the window with no A/c .
All you have to do is put the defrost switch half-way between foot and Defrost. The A/C will not come on. This causes the air to blow on the feet, side windows, and front windshield. If you don't believe me, try it, then turn the knob to the right to the defrost, and listen to the A/C come on. :w00t:
Now the complicated part. If it does fog up, push the A/C button, or turn the dial to defrost...:thumbsup:
I searched for this solution, did not see it, so if it is already done, sorry
b K