AC running when off

I've noticed that my AC runs on my 07 Tacoma 4 cyl 2wd Manual when A/C is off, temp is set to cold, vents set to defrost and circulation is from the outside. I've not gone through all the settings to see if there is a difference.

Anyone else experience this? Is there a recall?

I'll take it to the dealer but would like more info so I don't get bent over.

This may explain why I've not broken 20+ mpg on the truck.

Also the vents smell if I run the AC and let it sit. I've read a little about this, seems to be common with Toyota. :

 

I can see the heater working when set to hot, it's suppose too and there isn't a compressor involved.
But unless I push the A/C button, the cold air shouldn't be any colder then the air inside or outside depending on the setting.

 

If you have the vent set to any defrost position the A/C is designed to come on if the A/C switch is on or not. It is designed that way.

 

So I could stop my windshield from fogging from the inside in the winter by this feature. Good to know if my heater core every goes and both my windows won't roll down. Me being sarcastic.

But it's good to know cause I usauly left the control on defrost and outside air. I like to pull the outside air in with out all the noise from open windows and in the older cars you had a vent setting.

Are there any other settings which the A/C would still run?

 

This is true. The A/C will run when the AC button is pressed or the vent selector is on defrost. The idea behind the defrost setting is that the A/C will remove the moisture from the air...

As the air passes over the super cooled A/C coils the moisture falls out of the air due to condensation. That moisture is then drained out of the cab (ever see the pool of water under your truck?). Now the air will pass over the heater coils. Depending on the temperature setting on your dash, a valve allows certain amount of engine coolant to pass into the heater coils. The air will now be heated by these coils before it passes through the vents into the cab.

The defrost setting is will remove the moisture from the air, and depending on the temperature setting it will help defrost ice formed on your windows and windshield. Unfortunately, Toyota designed it to be "dummy proof". There is no easy way to disable the A/C with the defrost on.

 

This is true for all vehicles. you tacoma is no different from any other vehicle on the road.. you have nothing to worry about

 

Thats one feature about my truck that i dont like. I also like to just have my defrost on w/o the compressor kicking on, its a waste of gas if you dont actually need the AC on.

007: Are you saying that if i have the defrost on with the heat on it still uses the AC to take moisture out of the air? That doesnt sound right but thats what it sounded like on your post

 

I'd like to hear more about this. Yesterday on the drive home we had rain and I was running the defroster and the wipers on high (both of these were for the first time in my truck). I was stopped at a red light and I started smelling something like melting plastic. I turned the fan speed down and the wipers off and the smell gradually went away, but I was also moving away from the red light too. I'm not sure if it was my truck causing the smell or someone else at the red light near me.

 

When you turn on the defrost the A/C compressor kicks on but all you have to do is hit the A/C button and turn it off (at least that works on my truck).

 

How many miles you got on your truck? I've read a lot about people have weird odors emanating from their A/C while it was still breaking in, it should eventually go away.

 

Not many. I'm still under 1K. I won't lose sleep over the odor yet. I've been using the regular AC a good bit and haven't noticed any smell. I only noticed it in defrost mode yesterday.

 

Actually not all. It was true for my 94 Suburban and my 01 Accord, but not my:

93 Legacy
89 Accord
88 Accord
92 Saturn
98 Jetta
82 Rabbit
...

You get the point.

 

There's used to be a distinction between defrost and defog. Defrost used heat to melt ice on the windshielf. Defog uses the AC to remove humidity. I think nowadays those two purposes just depend on the temperature setting. Or maybe it's always defog and the heat setting just helps with ice too.

 

All i know, is that i would love to find a way to keep the compressor from kicking on when i turn on the defroster, it's annoying. If i want the AC and the defroster on at same time i'll twist the dial and then push a button, i dont want them permanantly linked. If anyone knows how to "unlink" the two that would make a great DIY thread..... hint hint

 

nd, didja miss this post?

 

I'd suspect that since you are a Texan (actually no smart ass joke here), and it's hot down there and you recently bought your truck, you have had no occassion to have your temp dial set anywhere but extreme cold, you would not have noticed it yet. There is a coating on heating parts that had to burn off the first time they are used. This is true for home as well as auto HVAC parts. That odor will dissapate within the first few times you use the heat or defrost.

Not that I doubt you TRDeity, but this seems more like coincidence than anything else, but I'll have to go out to my truck tomorrow and try it to see.

007 did a pretty good job of explaining all this, but here's how it breaks down. AC works by removing moisture from the air exactly as 007 described, and then passes the now dry air over the cold coils which is how the air coming out of you home or car vents is cold. When you have the defroster engaged as far as the engineers are concerned you have condensation (frost is just frozen condensation) on your windshield. The truck runs the ac to take the mositure out of the air that is going through the system so that when that same air hits the windshied it is free to take some of the moisture with it as it passes over other surfaces. (A buddy of mine is an HVAC tech and explained all this to me not that long ago while installing the new ultra high efficency condenser and furnace in my house)

As far as how to disable it? I've got nothing there. as any of you who have taken your HVAC controlls out to get to you radio know, your controlls are drive by wire. Old controlls worked like an old school friction type bicycle shifter and a stiff dial pulled a cable to controll the blend door (amount of hot to cold air entering the system) and a second one to controll the vent damper (which set of vents the air was directed to.)

Best guess would be to figure out how to get to the door controlling the defroster vents and disconnect the computer controlled rod and put in something like a manual choke cable or lawnmower throttle cable and be-able to open those vents while your selector switch was on something else. But that would prolly look pretty half-@$$ed.

 

I've been turning the A/C on deliberately when defogging, because I was under the impression that the manual said to for quicker defogging, for the reasons well explained in several earlier posts. I was so bothered by this that I actually got off my ass and got the manual out of the truck and checked. Sure nuff, page 241 2007 Tacoma Owner's Manual does say to "press the A/C button for dehumidified heating or cooling. This setting clears the front view more quickly."

But if it's already on, why turn on the A/C? And am I actually turning the A/C off and slowing my defog?

Help?