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TacomaGeneral discussion forum for the 2005 and later Toyota Tacoma.
This is a discussion thread titled "Defroster-linked Air Conditioning", within the Tacoma forum, part of the Truck Forums category.
The first picture is the pressure sensor located in front of the Power Steering Reservoir.
The second picture is a more convenient place to place a switch in the pressure sensor wire.
I've provided links to the wiring diagrams at the bottom so you can familiarize and verify.
Switching this wire will not give a fault code. When I unplugged the connector at the sensor, no "Check Engine" light, no fault code stored in my ScanGauge.
This is connector plug IA1 located behind the left kick panel. If you remove the kick panel, you'll see the large rectangular connector toward the top. The pressure sensor wire is at pin 32, about where I put the arrow. Sorry, I could not take the picture, shine the light and seperate the wires to display the orange pressure sensor wire. You can verify the correct orange wire as the one to the right is green and the one to the left is green/yellow. This orange wire is the one to switch. It should be convenient enough to locate a switch from here rather than running wire from the sensor.
NOTE: All page numbers are as in the manual (not the pdf page #)
Then finally, in this link, scroll down to page 300 to see the IA1 connector. As you are comparing the connector on your truck to the diagram, look to the left half (female side) of the diagram for the location of pin 32. http://www.ncttora.com/fsm/05+/data/...k/em01d0up.pdf
As far as installing the switch and locating it, your on your own as I have no intention of actually doing this, I just thought it would be interesting to find out how.
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Keezer
Silver '05 DC Short Bed 4x4 Auto w/Tow Package
Donahoe Coilovers & UCA's up front
Wheeler's Add-a-Leaf out back
Demello Rock Sliders
FJ Steel Wheels & Nitto P265 TerraGrapplers
You know, I'm still not sure what all this excersise is about. Today I tried turning the Fan, and Defroster on, with temp knob on heat. Outside air temp 40 F. I was sitting IN the cab.. actually at a traffic light. My ScanGuage registered an increase of maybe 130 RPM. I did this a few times and the response was pretty much the same. When I got home I tried it again, this time with the hood open. I could NOT get the compressor to run at this point.
First of all, I expected to see the center hub of the compressor turning. It was not. The belt and pully was freely turning but the clutch was not engaged...as far as I could tell.
Does the Center HUB of this design turn with the pully when engaged??
Since I could NOT get the RPM Increase to "Repeat" after the first couple of times, I think the compressor WAS SATISFIED that it had done it's duty by turning over a few times to lubricate the seals and then went to SLEEP again. The A/C Button Light did NOT come on during any of this testing..... UNTIL I turned it on to see if the compressor would turn over, either in A/C COOL or otherwise. I think this whole system may be Smarterthan we might think. TacoGuy
Wow! I stand corrected! This is really shocking - a GM air conditioning system in a Toyota! The Nippondenso compressor in my 1992 Toyota is still going strong after 471,300 miles and so is the one in the 1974 Celica. No GM compressor can do that. Example: The GM compressor in my long gone 1982 Pontiac self destructed at 120,000.
It will be interesting to read the April 2008, 2009, 2010 & 2011 issues of Consumer Reports to see how the reliability of the 2005 Tacoma HVAC system has fared with GM parts
Wow! I stand corrected! This is really shocking - a GM air conditioning system in a Toyota! The Nippondenso compressor in my 1992 Toyota is still going strong after 471,300 miles and so is the one in the 1974 Celica. No GM compressor can do that. Example: The GM compressor in my long gone 1982 Pontiac self destructed at 120,000.
It will be interesting to read the April 2008, 2009, 2010 & 2011 issues of Consumer Reports to see how the reliability of the 2005 Tacoma HVAC system has fared with GM parts
From what they said in the article ("Already enjoying a long-standing history of supplying engine cooling components to Toyota, this is the first Delphi-produced HVAC systems featured on a Toyota-branded vehicle."), it sounds like the cooling was already in the older Tacomas. What's new is the whole HVAC system (and a newer compressor model). So, maybe not much change in durability/longevity. Three years of solid use and no problems at all here.
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"It's not what you know. It's knowing where to find the answer."
'05 4x4 DC LB SR5 Tow Pkg BFG All-Terrain T/A KO, Leer Tonneau, Westin Platinum Nerf Bars, Fog Light Mod, Orig. Owner 12/3/04
Since I could NOT get the RPM Increase to "Repeat" after the first couple of times, I think the compressor WAS SATISFIED that it had done it's duty by turning over a few times to lubricate the seals and then went to SLEEP again. The A/C Button Light did NOT come on during any of this testing..... UNTIL I turned it on to see if the compressor would turn over, either in A/C COOL or otherwise. I think this whole system may be Smarterthan we might think. TacoGuy
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2006 Pre-Runner TRD Access Cab V6
with 60mph vibration
Does the Center HUB of this design turn with the pully when engaged??
Yes it does.
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"It's not what you know. It's knowing where to find the answer."
'05 4x4 DC LB SR5 Tow Pkg BFG All-Terrain T/A KO, Leer Tonneau, Westin Platinum Nerf Bars, Fog Light Mod, Orig. Owner 12/3/04
I'm not positive, but I'm pretty sure the compressor should not engage when the outside temperature is below 45 degrees or so. This should be true whether you turn on defrost or AC. Most car AC systems have a low pressure cutout switch that will turn the compressor off when the outside temp is 45 or lower.
So, if that's true, it may not be worth disconnecting it if you live in a cold climate, because it may not be running anyway.
On previous generations of Toyotas with genuine Nippondenso air conditioning components (as opposed to present day Delphi - GM components) the compressor would operate all the way down to near 32 degrees F. So interior windshield defogging was still excellent when outside temps were in high 30's and low 40's.
I have been using a very simple solution to this problem. Go under the hood and pull the fuse for the A/C unit. Now it will not work when you press the button but in two winters in Seattle of testing, it makes little difference whether the compressor runs or not to help defrost the windows. And I can attest to the comp running in subfreezing weather. It runs! Also another side benefit is that when the comp kicked in, unless the heat was at max, the airflow got colder. Now no real need to readjust the temp. And engineers can make mistakes as nobody is perfect.
I'm not positive, but I'm pretty sure the compressor should not engage when the outside temperature is below 45 degrees or so. This should be true whether you turn on defrost or AC. Most car AC systems have a low pressure cutout switch that will turn the compressor off when the outside temp is 45 or lower.
Kathyricks is right that it does work in colder temperatures. I haven't checked when it's been in the low 20s but it definitely runs in the upper 20s and low 30s when I've needed to evaporate the condensation that builds on the windshield behind where the snow is frozen to the glass.
Just a FYI it's recommended to run the A/C even in the winter for at least 10 minutes a week to keep the O rings lubricated and to keep the refrigerant and oil mixed rather than have the oil sitting in a low point in the system where it would do no good.
I do have to admit I do not like that I can't control when it does and doesn't run but for the average person having the A/C run in defrost is the only time the oil gets a chance of being circulated in the system.
Pulling the fuse and not running the A/C at all during the winter is setting yourself up for problems when summer comes around. Just my .02.
Just a FYI it's recommended to run the A/C even in the winter for at least 10 minutes a week to keep the O rings lubricated and to keep the refrigerant and oil mixed rather than have the oil sitting in a low point in the system where it would do no good.
I'll be the first to admit that much of the expertise in this thread has been above me... but the above statement makes good sense to me. My old Chevy lost all its freon many years ago because the front compressor seal expired -- possibly from lack of use, though the truck is my DD. If occasional cycling helps extend the life of the system, I'm all for it. If it costs me a few more pennies for gasoline, so be it. I am not chasing every tenth of a mile-per-gallon, or I would not have bought the Tacoma in the first place.
Honda has a good solution to this DEF-linked A/C debate: Automatic A/C on and REC off when DEF is selected. User can then override A/C and REC by press the buttons.
Just a FYI it's recommended to run the A/C even in the winter for at least 10 minutes a week to keep the O rings lubricated and to keep the refrigerant and oil mixed rather than have the oil sitting in a low point in the system where it would do no good.
I do have to admit I do not like that I can't control when it does and doesn't run but for the average person having the A/C run in defrost is the only time the oil gets a chance of being circulated in the system.
Pulling the fuse and not running the A/C at all during the winter is setting yourself up for problems when summer comes around. Just my .02.
This is an important consideration and a good reason to not attempt to modify the system by disconnecting wires or installing extra switches. Living in Maine, with a car where the AC was not automatically linked to the defroster, it wasn't unusual to go several months without lubricating the seals by "exercising" the air conditioning compressor. I learned the importance of this the hard way ($600) when I had to buy a new compressor for my 37 month old Volvo 240.
The energy it takes to run the compressor is pretty small compared with the total output of the engine, and especially when you stop and think about what percentage of the time you have defrost selected (usually just when warming up the car unless it's snowing or raining out) , it seems to me that the fuel savings to be gained by being able to shut off the compressor manually is trivial compared with the potential expense of buying a new one. The engineers have considered all this and designed the system so all of you don't have to buy a new compressor in order to learn this lesson the hard way. But if you insist...
More effort should be put forward in cracking the code in the ECUs of the Tacoma. The 1GR runs especially rich, and I can just imagine how much more fuel is dumped into the cylinders during the cold start enrichment program. I checked my new iridium plugs after about 1500 miles, all with cold starts, and the rim is covered in soot, leading me to believe the mixture is quite rich, as a lean mixture leaves no residue and is quite hot and powerful.
I believe that leaning the engine out will enhance our gas mileage and power more than delinking the A/C from the defroster.
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Re: Defroster-linked Air Conditioning
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Linear Mode
