Any ideas on how to remove "idiot proofing" in my van's climate control?

[HowAboutThis]

First Gen Toyota Sienna. Good van! Although, the climate system has been made stupid by idiot-proofing several features.

Here's the problem. When the control knob is set to defrost, it automatically turns on the AC system and opens the recirc vent. I would like the option to turn on the defrost windshield blower ports, but NOT open up the recirc vent and turn on AC. It's just not needed when a little warm air is all that it takes to keep the glass from fogging up. I don't like the idea of wasting my AC system and gas when it is not needed. I also prefer to have the van on recirculate mode when in traffic or behind stinky diesel monster trucks rolling coal everywhere.

Ideally, the system should just allow for changing the blower vents without automatically opening the recirc and turning on AC. If I want a combo, I can just hit the buttons I want for that combo. The way Toyota idiot-proofed the system makes it less ideal for people who know how to press two buttons instead of just turning a dial.

I was thinking of taking the dash apart and either disconnecting the AC wire going to the relay or cutting it, and also seeing if I can dismantle the mechanism that opens the recirc. I would leave the AC and recirc buttons alone and keep them operational. Only the automatic mechanism in the vent dial needs to be modified.

Any thoughts on whether this would be the best plan of attack? Any ideas on doing this without removing the dash? It's not really that hard, but is more involved than other dashes I have taken apart.

Here's the setup.

View attachment 37880

My old 02 Civic had a hack where you pressed a couple of the HVAC buttons and held for a certain number of seconds to toggle those features on and off. If you Google, you might find your system has something similar.

 

[HowAboutThis]

First Gen Toyota Sienna. Good van! Although, the climate system has been made stupid by idiot-proofing several features.

Here's the problem. When the control knob is set to defrost, it automatically turns on the AC system and opens the recirc vent. I would like the option to turn on the defrost windshield blower ports, but NOT open up the recirc vent and turn on AC. It's just not needed when a little warm air is all that it takes to keep the glass from fogging up. I don't like the idea of wasting my AC system and gas when it is not needed. I also prefer to have the van on recirculate mode when in traffic or behind stinky diesel monster trucks rolling coal everywhere.

Ideally, the system should just allow for changing the blower vents without automatically opening the recirc and turning on AC. If I want a combo, I can just hit the buttons I want for that combo. The way Toyota idiot-proofed the system makes it less ideal for people who know how to press two buttons instead of just turning a dial.

I was thinking of taking the dash apart and either disconnecting the AC wire going to the relay or cutting it, and also seeing if I can dismantle the mechanism that opens the recirc. I would leave the AC and recirc buttons alone and keep them operational. Only the automatic mechanism in the vent dial needs to be modified.

Any thoughts on whether this would be the best plan of attack? Any ideas on doing this without removing the dash? It's not really that hard, but is more involved than other dashes I have taken apart.

Here's the setup.

View attachment 37880

No idea if something similar for a Sienna, but supposedly this works for a Tacoma...?

Defrost without A/C mod

Hello TacomaWorld I can't remember where I saw someone say this, but I didn't see a write up for it anywhere so I thought I'd make one. When you turn...

www.tacomaworld.com

 

[MrPlow]

Most people here feel you're trying to fix something that isn't broke. Saying, "it just makes it take longer to heat up as it fights the heater core" isn't true as most compressors don't kick in below 40F anyway, and if they did, the longer time to heat up is marginal. And saying, "I don't like the idea of wasting my AC system and gas when it is not needed" is also flawed as the amount of extra gas you use idling might be a few cents. If it really bothers you, put an on/off switch in the dash wired to the compressor so you can keep it off at will.

It does actually engage the AC compressor and cools the air even when below 30F inside the van. It does take longer to melt the windshield and it does cool the air considerably when on. This is fact. I have the van. I have tested it.

I do use the AC during the winter on a regular basis, just not 100% of the time I am driving the van if not needed.

 

[MrPlow]

No idea if something similar for a Sienna, but supposedly this works for a Tacoma...?

Defrost without A/C mod

Hello TacomaWorld I can't remember where I saw someone say this, but I didn't see a write up for it anywhere so I thought I'd make one. When you turn...

www.tacomaworld.com

That's very interesting!

Thanks for posting that. I'll see if the knob pulls off on my van.

 

[MrPlow]

I'm going to take the dash apart today if I get a chance and the weather clears up a bit.

On a separate note, why are people so paranoid about the AC system drying out and going bad? I have literally never even had to have my AC serviced at all in any vehicle I have ever owned. In fact, in my lifetime, neither has my dad or any immediate family that I can think of. The only one I had that didn't have AC is my truck which never came with any AC system to begin with.

Every vehicle I have owned with AC had it decoupled from the vent system. If you wanted air on the windshield, then you set to have air on the windshield and then choose to have AC running as an option. I never, ever used the AC all the time in any of my cars. In fact, it would actually be off most of the summer in nice weather where AC isn't needed on mild days.

So, where exactly did the "your AC system is going to die without constant use" boogyman come from? Am I just lucky? Maybe the temperate climate I live in isn't hard on AC systems? I'm genuinely curious, as AC system failures seem to have been exceedingly rare for people around where I live. We also often have regular car batteries that last 10 years, where as the same ones in Arizona wouldn't last 3 years at most. Besides rust, car parts tend to last a longer time in our mild climate in Washington state.

 

[atikovi]

Besides rust, car parts tend to last a longer time in our mild climate in Washington state.

Then it sounds like you don't use the a/c much which is why it doesn't need service. I drive around with it off even on miserable hot days on any older car I'm going to sell, worrying it will break down before I do. Probably not justified though.

 

[PimTac]

Then it sounds like you don't use the a/c much which is why it doesn't need service. I drive around with it off even on miserable hot days on any older car I'm going to sell, worrying it will break down before I do. Probably not justified though.

I live in the same area and we use the A/C quite a bit. The damp environment is the reason for using the air conditioning. The windshield defogs itself very quickly.

 

[MrPlow]

I live in the same area and we use the A/C quite a bit. The damp environment is the reason for using the air conditioning. The windshield defogs itself very quickly.

AC does awesome when it's raining and 40 degrees outside and we get in the van all wet. No question about that.

When it's just a matter of keeping the windshield from getting a little fogged up from my breath and sweat, and it's mostly dry and/or warmer, the AC is not necessary.

 

[Blinker]

I'm going to take the dash apart today if I get a chance and the weather clears up a bit.

On a separate note, why are people so paranoid about the AC system drying out and going bad? I have literally never even had to have my AC serviced at all in any vehicle I have ever owned. In fact, in my lifetime, neither has my dad or any immediate family that I can think of. The only one I had that didn't have AC is my truck which never came with any AC system to begin with.

Every vehicle I have owned with AC had it decoupled from the vent system. If you wanted air on the windshield, then you set to have air on the windshield and then choose to have AC running as an option. I never, ever used the AC all the time in any of my cars. In fact, it would actually be off most of the summer in nice weather where AC isn't needed on mild days.

So, where exactly did the "your AC system is going to die without constant use" boogyman come from? Am I just lucky? Maybe the temperate climate I live in isn't hard on AC systems? I'm genuinely curious, as AC system failures seem to have been exceedingly rare for people around where I live. We also often have regular car batteries that last 10 years, where as the same ones in Arizona wouldn't last 3 years at most. Besides rust, car parts tend to last a longer time in our mild climate in Washington state.

I can tell from your attitude that you won’t last long here. To answer your question, back in the 70’s-80’s it was very common for people to unplug the electrical connector to the A/C compressor during the winter time. A lot of people felt it wasn’t necessary to run the compressor in the winter. Running the A/C compressor helps keep all the seals pliable in the refrigerant lines.

 

[MrPlow]

So, I did the AC part of the equation. It took longer for my dog to find a spot to poop than it did actually removing the AC automatic switch from the vent dial mechanism. LOL

I took the radio out and got lucky! The AC activator switch is located on the bottom of the climate control unit. First, it took a couple screws to just remove the radio and some pop-in panel plastic.

From there, I was able to locate the plastic mechanism that is pushed in to activate the AC when the vent dial is set to defrost setting. I tried taking the wiring plug off, and this turned off the AC, but also turned off the other controls, along with the manual AC button. Instead of jumping wires and stuff to see which one I needed to cut, I decided to leave the wiring alone and just remove the piece that turns on the AC from the dial.

The wiring is located in the green circle. The plastic push rod thing is in the red circle. As the plastic under the large white unit rotates, it pushes the black piece in to engage AC.

I used a sawsall blade and cut the black plastic tab off by hand. It was a pretty clean cut even though room was very limited. I put a napkin down to catch the shavings.

AND BOOM! My main issue with the system has been resolved! I still have to find a way to prevent the recirc door from openeing when the vent dial is turned, but I can work around that by just activating it manually when I need to keep it closed due to diesel exhaust coming in. Getting there is going to require taking apart more of the dash, so I will wait until I have some dash light bulbs so I can do all the work at the same time.

I can now have my windshield defrost vents going without AC automatically going on the whole time. I can also now manually press the AC button to get AC going when I need extra oomph in clearing the windshield.

 

[MrPlow]

I can tell from your attitude that you won’t last long here. To answer your question, back in the 70’s-80’s it was very common for people to unplug the electrical connector to the A/C compressor during the winter time. A lot of people felt it wasn’t necessary to run the compressor in the winter. Running the A/C compressor helps keep all the seals pliable in the refrigerant lines.

Again, I am not going the whole winter without using AC. People keep arguing against an imaginary straw man who isn't going to ever run AC. Not implying you are saying such, just in general.

I personally think it would indeed be stupid to turn off AC all winter and never use it. It's incredibly useful when needed! But it isn't always needed and it's nice to have control over that.

Plus, this forum isn't anywhere close to as hostile as many other forums out there. Every forum has abrasive people who just want to be contrary and mean without offering much help or who choose to be intentionally obtuse and not read what is actually be said.

C'est la vie.

 

[eljefino]

OP is correct for seeking control. It's his vehicle that he owns. I did this on my 1992 cutlass ciera.

That car had "flow through ventilation" whether I wanted it or not, and it landed on my feet. The only way to keep cold air off my feet, when first driving a cold engine, was to select defrost. This, however, turned on the AC compressor, and it would fog up on the outside of my windshield due to the cold glass. Remember, AC comes on instantly but the heater core takes a few minutes to warm up.

A toggle switch cured all my problems.

 

[cvlw]

On my 2013 Mazda 6, when I turn the temp dial all the way down to the coldest setting, it auto-annoyingly turns on max AC.
I hate that "feature." The manual says it is supposed to do this and the solution is to just turn off AC.
I despise having to turn off the AC only after a couple of seconds.
Like the poster, I want to be able to determine when the AC is on, in this case, when I want nothing more than the coldest vent.
The second-coldest notch on the temp dial puts out slightly warmer air, so it isn't exactly what I want.

 

[MrPlow]

On my 2013 Mazda 6, when I turn the temp dial all the way down to the coldest setting, it auto-annoyingly turns on max AC.
I hate that "feature." The manual says it is supposed to do this and the solution is to just turn off AC.
I despise having to turn off the AC only after a couple of seconds.
Like the poster, I want to be able to determine when the AC is on, in this case, when I want nothing more than the coldest vent.
The second-coldest notch on the temp dial puts out slightly warmer air, so it isn't exactly what I want.

That year and model have electronic climate buttons doesn't it? Might be a lot harder to jury rig it to not engage AC.

This is kind of hacky, but I wonder if it would work to install a relay toggle switch in the cabin that disrupts the AC from turning on by itself?

 

[supton]

I *think* my '99 Camry has it isolated. Recirculate is a slider, no interaction with defrost. Not sure if a/c comes on with defrost or not, not sure I've tried, nor had a problem. Then again, in years past, I'd roll down a window in cold weather to prevent interior frosting problems, that doesn't bother me. Probably does come on with defrost, just never had an issue with that.

I prefer the controls to be separate too. Sometimes one gets an ice storm and the best thing to do is to simply start the car, turn on defrost and go back inside for a few--let it heat up, soften the ice, then it will scrape off with vastly less work. [No I don't let my car idle to warm up the rest of the time. Only for this scenario--it warms up faster if I just drive it. After a proper cleaning off of course.] There has been a few times on prior cars that I was miffed that turning to defrost would defeat recirculate. I'm not in the car, it won't get warm enough to fog anything up--and even if it did, I have three working brain cells and know how to fix the problem. Don't go thinking for me!

 

[Aredeeem]

OMG, I thought I was bored. What’s next? Changing all the filaments in the Christmas lights?

 

[MrPlow]

Another benefit I have seen in my van the last couple of cold mornings is that the AC kills the warm air temp coming out of the vents, and having it off, while blowing on the windshield, I can keep the van warmer without turning on the rear heaters and blowers. The AC in the first gen Sienna vans is pretty powerful.

 

[MrPlow]

OMG, I thought I was bored. What’s next? Changing all the filaments in the Christmas lights? This is why I park at the far end of the supermarket parking lot.

For a vehicle enthusiast forum, there is a surprising number of people who loath the idea of modifying one's own vehicle to make it work they want it to work. It is a bit perplexing. LOL

Now, if I was pulling the entire dash apart to change the green light bulbs to a slightly different shade of green for vanity reasons, then I could understand the mockery. But, if you read my follow-up post, the alteration to my van was easier than changing the engine oil, by an order or magnitude. (not literally) Couple fasteners, cut a little chunk of plastic, and there is no downside to the alteration at all.

Wait until folks hear about how I cut the wire for the running lights that run all the time, and installed a toggle switch so I can idle the car at night without lights on and not use up electricity and bulbs running them on bright sunny days.

 

[Aredeeem]

I get it, my sarcasm comes from envy. Just because I never could certainly doesn’t diminish your enthusiasm and abilities. Well done.

 

[cvlw]

That year and model have electronic climate buttons doesn't it? Might be a lot harder to jury rig it to not engage AC.

This is kind of hacky, but I wonder if it would work to install a relay toggle switch in the cabin that disrupts the AC from turning on by itself?

It is the three dials with the centers as push buttons. When the temp is turned to lowest dial setting, it turns on max AC which is AC plus recirc.
Yeah, it is probably not a simple hack-around. Someday.... someday...