Shut down the AC for winter

[jimmi]

After reading around the forums, so far the only way to shut down the AC for winter is .... pull the realy. I tried the fuse: This does a number of things. It sets the "Check Engine! lamp on, and, upsets the TCM (transmission control module) - will not change into 5th. (Fix: replace fuse, disconnect battery for 30 secs then reconnect. Oh, BTW, you may now need to "retrain" you tranny (per other posts).

Why do this? The moment your air control moves to the floor vents only position the A/C compressor comes on. Even down to freezing temperatures. the owners manual gives some value where the ECU decides this should no longer happen, but, at 28deg F I really do not need any A/C. Usually the purpose of this is to dry the incoming air that may be directed at the winshield to improve de-fogging.

I carried out a futhere investigation of the A/C control module behinf the panel to see if another switch could be added. This is no simple device. The temperature control is purely mechanical, the fan speed a simple switch. However, the air-flow control was obviously designed by a "NASA" scientist. This finely stepped device is a potentiometer (like a volume control on a radio) that is input to what appears to be a small computer chip. By the looks of things, it may even be a CANBUS device.

Anyone with a better idea or have a schmatic of this area please post.

[burnout]

I removed the A/C relay. No engine lights or anything, but there is one small problem. If I have the defrost on, or the floor setting, I can hear the condenser fan kick on, even though the compressor is not running. The car thinks that it is running so it turns on the fan even when I'm driving, but it isn't. I don't particularly like this because it could cool the engine down below operating temperature. I use the defroster briefly before the computer decides that the fan needs to be on for some odd reason.

[OhioVueBoy]

It turns off by itself below 40*F.

You do realize that the A/C turns on with the defroster to dehumidify the air, rather than cool it, don't you?

~D.J.~

[burnout]

Yeah I know it goes on to dehumidify the air, but my defroster works perfectly without the A/C. My skin is dry enough from the hot air in the car :-P

Also: My compressor turns on below 40º I believe. I'll have to double check. Maybe I'm being paranoid about the gas mileage hit.

[05vueblue]

A simple solution is just run it on the vents. I hate the floor vents on make my feet sweat. I just used defroster long enought to do its job then I shut off. has any one figured out how much miliage really suffers with compressor on? I know at WOT it kick out doesnt it? was curious about that.......

[Bullet]

As far as I know from past experiences is, if you dont run the air in the winter seals dry up and then the freon will leak out. I wouldnt mess with anything and I do run the air when ever it is above 40* once in a while just to keep all parts moving. ;)

[Tom92SCm]

Maybe I'm being paranoid about the gas mileage hit.
It's winter time. Mileage goes down in the winter. Don't like it? Move south.

--Tom

[bigc791]

The ac is run because it does a great job of getting moisture out of the air. Also it keeps everything lubricated. That oil in the system needs to circulate to keep the compressor lubed up
Carmen

[PlumSL1]

Shutting off your A/C for the winter could lead to costly problems. I would just live with it.

[99blacktop]

It says it doesn't come on below 40 degrees, but that isn't always the case, I have heard mine kick on in the low 30s before.

Yes, you should run the a/c once in awhile to keep everything running smoothly, but there is no need to run it all the time. I like to keep my feet warm and/or let the air blow over my head instead of in my face, there is no need to run the compressor because of that. Besides, the act of heating the air removes the humidity, there is no reason to force the a/c upon us and lower gas mileage and engine power, especially for us 4 cylinder owners. If they want to force it upon us, they should at least provide a way to turn it off when the driver determines that it is not necessary.

I normally just keep my fan off and let 'flow thru' keep the warm air moving. I love the fact that I can direct the air at my feet and/or windshield in my SC2 and not kick on the compressor. That is just a waste of energy and extra wear and tear on the components.

I'm all for computerizing the car where it makes sense, but I miss the days when it was actually my responsibility to control the various functions within the car.

[wolfman]

Shutting off your A/C for the winter could lead to costly problems. I would just live with it.

You are absolutely CORRECT about that.... The A/C compressor will only cycle during cold weather when the front windshield DEFROSTER is on...when it (A/C function) is NEEDED to dehumidify the air inside the car and prevent window fogging. A compressor at REST (disenegaged) simply freewheels just like the idler and tensioner pulleys. There is absolutely no reason to "shut down" the A/C system for the winter by monkeying around with the car. Occasioal use of the A/C during winter months is RECOMMENDED by the manufacturer (read your owner's manual!) and keeps oil circulated in the A/C system, prolonging the componants life.

[wolfman]

Shutting off your A/C for the winter could lead to costly problems. I would just live with it.

You are absolutely CORRECT about that.... The A/C compressor will only cycle during cold weather when the front windshield DEFROSTER is on...when it (A/C function) is NEEDED to dehumidify the air inside the car and prevent window fogging. A compressor at REST (disenegaged) simply freewheels just like the idler and tensioner pulleys. There is absolutely no reason to "shut down" the A/C system for the winter by monkeying around with the car. Occasioal use of the A/C during winter months is RECOMMENDED by the manufacturer (read your owner's manual!) and keeps oil circulated in the A/C system, prolonging the componants life.

[wolfman]

Shutting off your A/C for the winter could lead to costly problems. I would just live with it.

You are absolutely CORRECT about that.... The A/C compressor will only cycle during cold weather when the front windshield DEFROSTER is on...when it (A/C function) is NEEDED to dehumidify the air inside the car and prevent window fogging. A compressor at REST (disenegaged) simply freewheels just like the idler and tensioner pulleys. There is absolutely no reason to "shut down" the A/C system for the winter by monkeying around with the car. Occasioal use of the A/C during winter months is RECOMMENDED by the manufacturer (read your owner's manual!) and keeps oil circulated in the A/C system, prolonging the componants life.

[piney]

You are absolutely CORRECT about that.... <snip>


I got the point after the first post but the added emphasis of three times makes me a true believer.

[burnout]

The A/C in a vue turns on in THREE of the five positions for vents. THREE!

Thats why I took my relay out. I put it in recently just to see if it would come on when its cold, and sure enough, when its 28º out.... I see the idle jump and hear the compressor kick in.

Toasty feet shouldn't = bad gas mileage. I WISH it was only the defroster setting that turned the A/C on.

[ssicarman]

The following is from the 2005 service manual.
You may want to note he section in red. If your compressor is kicking in at 28 degrees F then you have something not right. I would suggest taking it to Saturn if your are still under warrenty. If not then or before you do check the wiring connector from the TXV. Make sure that it is plugged in properly. It is on the engine side of the AC lines where then go through the fire wall. There will be wires from TXV at the fire wall to a connector.

I would think that between this temp sensor and the pressure sensor your system should not normally work at the temps that you are now getting.

Also note the compressor description. The compressor being a variable displacement compressor will under low load conditons, think low ambient temps, not take much power to run.



Air Temperature Description and Operation


A/C Refrigerant Pressure Sensor
The A/C refrigerant pressure sensor is a 3 wire piezoelectric pressure transducer. A 5-volt reference, low reference, and signal circuits enable the sensor to operate. The A/C pressure signal can be between 0-5 volts. When the A/C refrigerant pressure is low, the signal value is near 0 volts. When the A/C refrigerant pressure is high, the signal value is near 5 volts.

The A/C refrigerant pressure sensor protects the A/C system from operating when an excessively high or low pressure condition exists. The engine control module (ECM) or powertrain control module (PCM) disables the compressor clutch under the following conditions:


L66/3.5L

The A/C high side pressure is more than 2929 kPa (495 psi). The clutch will be enabled after the high side pressure decreases to less than 1376 kPa (200 psi). A/C low side pressure is less than 2706 kPa (39 psi). The clutch will be enabled or will allow engagement again after the low side pressure increases to more than 2941 kPa (43 psi).



Evaporator Low Ambient Protection
The refrigerant temperature at the temperature sensor in the thermal expansion valve (TXV) controls cycling of the compressor clutch to prevent freezing of the evaporator core. The compressor is disabled when the temperature goes below 3°C (37°F) and vehicle speed is greater than 8 km/h (5 mph). The compressor is enabled when the temperature exceeds 4°C (40°F). The minimum cycling time off is 4 seconds.



Heating and A/C Operation
The purpose of the heating and A/C system is to provide heated and cooled air to the interior of the vehicle. The A/C system will also remove humidity from the interior and reduce windshield fogging. The vehicle operator can determine the passenger compartment temperature by adjusting the air temperature control. Regardless of the temperature setting, the following can effect the rate that the HVAC system can achieve the desired temperature:

• Recirculation

• Difference between inside and desired temperature

• Difference between ambient and desired temperature

• Blower motor speed setting

• Mode setting

The vehicle operator can activate the A/C system by pressing the A/C switch. The A/C system can operate regardless of the temperature setting.

The ECM/PCM will operate the A/C system automatically in FRONT DEFROST mode to help reduce moisture inside the vehicle. The A/C LED will not illuminate unless the driver presses the A/C request switch on the HVAC control module. The MAX A/C selection will force the HVAC system into recirculation and show A/C ON LED status. The A/C system maybe running without the A/C LED indicator illuminated when in FRONT DEFROST mode. The HVAC system uses a compressor that incorporates a thermal switch that opens once the compressor temperature exceeds 211-217°C (380-454°F) creating an open circuit.

Once engaged, the compressor clutch will be disengaged for the following conditions:

• L66/3.5L--Throttle position is 100 percent

• L66/3.5L--A/C pressure is more than 2929 kPa (495 psi).

• L66/3.5L--A/C pressure is less than 2706 kPa (39 psi).

• L66/3.5L--Engine coolant temperature (ECT) is more than 120°C (248°F).

• L66/3.5L--Engine speed is more than 6,240 RPM.

• Transmission shift

• ECM/PCM detects excessive torque load.

• ECM/PCM detects insufficient idle quality.

• ECM/PCM detects a hard launch condition.

When the compressor clutch disengages, the compressor clutch diode protects the electrical system from a voltage spike.


Engine Coolant
Engine coolant is the key element of the heating system. The thermostat controls engine operating coolant temperature. The thermostat also creates a restriction for the cooling system that promotes a positive coolant flow and helps prevent cavitation. Coolant enters the heater core through the inlet heater hose, in a pressurized state.

The heater core is located inside the HVAC module. The heat of the coolant flowing through the heater core is absorbed by the ambient air drawn through the HVAC module. Heated air is distributed to the passenger compartment, through the HVAC module, for passenger comfort.

The amount of heat delivered to the passenger compartment is controlled by opening or closing the HVAC module air temperature door. The coolant exits the heater core through the return heater hose and recirculated back through the engine cooling system.

A/C Cycle
Refrigerant is the key element in an air conditioning system. R-134a is presently the only EPA approved refrigerant for automotive use. R-134a is a very low temperature gas that can transfer the undesirable heat and moisture from the passenger compartment to the outside air.

The compressor is a variable displacement scroll type pump. The compressor uses a control valve to vary its displacement from 6.5 percent (9cc) to 100 percent (105cc). The A/C compressor is belt driven and operates when the magnetic clutch is engaged. A thermal protection switch is incorporated into the compressor. If the temperature exceeds 211-217°C (380-454°F), the switch will open creating an open circuit. The compressor builds pressure on the vapor refrigerant. Compressing the refrigerant also adds heat to the refrigerant. The refrigerant is discharged from the compressor, through the discharge hose, and forced to flow to the condenser and then through the balance of the A/C system. The A/C system is mechanically protected with the use of a high pressure relief valve located in the compressor hose assembly block. This valve will open at 3965-3375 kPa (575-490 psi), and reset at 2930 kPa (425 psi). If this valve ever opens the A/C system must be serviced and the valve must be replaced.

Compressed refrigerant enters the condenser in a high temperature, high pressure vapor state. As the refrigerant flows through the condenser, the heat of the refrigerant is transferred to the ambient air passing through the condenser. Cooling the refrigerant causes the refrigerant to condense and change from a vapor to a liquid state.

The condenser is located in front of the radiator for maximum heat transfer. The condenser is made of aluminum tubing and aluminum cooling fins, which allows rapid heat transfer for the refrigerant. The semi-cooled liquid refrigerant exits the condenser and flows through the liquid line, to the thermal expansion valve (TXV).

The TXV is located at the evaporator inlet and outlet pipes. The TXV is the dividing point for the high and the low pressure sides of the A/C system. As the refrigerant passes through the TXV, the pressure on the refrigerant is lowered. Due to the pressure differential on the liquid refrigerant, the refrigerant will begin to boil at the TXV. The TXV also meters the amount of liquid refrigerant that can flow into the evaporator.

Refrigerant exiting the TXV flows into the evaporator core in a low pressure, liquid state. Ambient air is drawn through the HVAC module and passes through the evaporator core. Warm and moist air will cause the liquid refrigerant to boil inside of the evaporator core. The boiling refrigerant absorbs heat from the ambient air and draws moisture onto the evaporator. The refrigerant exits the evaporator through the suction line and back to the compressor, in a vapor state, and completing the A/C cycle of heat removal. At the compressor, the refrigerant is compressed again and the cycle of heat removal is repeated.

The conditioned air is distributed through the HVAC module for passenger comfort. The heat and moisture removed from the passenger compartment will also change form, or condense, and is discharged from the HVAC module as water.

[Bullet]

The A/C in a vue turns on in THREE of the five positions for vents. THREE!

Thats why I took my relay out. I put it in recently just to see if it would come on when its cold, and sure enough, when its 28º out.... I see the idle jump and hear the compressor kick in.

Toasty feet shouldn't = bad gas mileage. I WISH it was only the defroster setting that turned the A/C on.


Thats a really dumb idea. I hope you are not that desperate for $$$.
The condenser is located in front of the radiator for maximum heat transfer.
So you live where it can get -20*+ and drive down I88 @ 75MPH.
What temperture do you think your condenser is then :eek:

You are not saving, you are surely killing your A/C. :ugh:

BulleT
:hmpf:

[mikebutkus]

Why not just put a relay between the power wire to the magnetic clutch..
A switch can be added to allow it to be on or off. Just use the switch to ground the relay to work. Easy enough. Not sure if the computer checks the freon sensor to see if it's making compression.
I'll have to check when the '04 air kicks in... on the two upper vent positions I can see but not on the forward vents nor feet position.

[1saxman]

"The A/C compressor will only cycle during cold weather when the front windshield DEFROSTER is on"

Totally false on the VUE. The compressor also cycles in the floor register position (starting on some '03s) except as controlled by temperature and speed as stated above.

[D C]

I'm still utterly confused by this whole thread. Are you people serious in that you expect to see fuel economy gains from disabling the A/C compressor in the winter? If you're that concerned about economy, why are you driving an SUV to begin with? And how long will you let a car sit and warm-up before driving it in the winter?

[99blacktop]

I'm still utterly confused by this whole thread. Are you people serious in that you expect to see fuel economy gains from disabling the A/C compressor in the winter? If you're that concerned about economy, why are you driving an SUV to begin with? And how long will you let a car sit and warm-up before driving it in the winter?I don't want to disable it in the winter, I want to disable it any time I haven't pushed the "a/c" button. There is absolutely no reason to run the compressor just because the vent is pointed at my feet and/or the windshield. If I am too hot, or feel that my windows need some help defogging, I'm perfectly capable of pushing the button.

I have yet to hear a good reason for the auto compressor. My SC2 has worked just fine for 7+ years and 99,950+ miles without it and my SL2 was still working great after 100,000+ miles when I traded it.

I don't doubt that there are some people who never use it and it's seized when they finally need it, but that isn't my problem.

[gerrysvue]

WHY BOTHER?? Sounds like a lot of work . There is a definate reason for the design.

[VUEnumber1]

My wife's Uplander has an "Instant MPG" indicator on the dash. When I turned on the defrost it went down 1 or 2 MPG.

Hardly worth the effort and effects of pulling the fuse, considering the amount of time the switch is on the positions that make the compressor turn on.

On my '03, I can put the dial on 'face' and give it a few clicks toward 'floor' and the compressor doesn't turn on.

[Dante]

My wife's Uplander has an "Instant MPG" indicator on the dash. When I turned on the defrost it went down 1 or 2 MPG.

Hardly worth the effort and effects of pulling the fuse, considering the amount of time the switch is on the positions that make the compressor turn on.

On my '03, I can put the dial on 'face' and give it a few clicks toward 'floor' and the compressor doesn't turn on.

I brought this up with the dealer techs a looong time ago... and that's basically what they told me... put it 1 click away from floor only towards mixed face/floor. This will keep the compressor from kicking on. Usually when it's cold here, it's not very humid, and simply heating the air dries it enough to where condensation isn't a problem. With as much as the doors leak cold air on the Vue, if I'm traveling highway speeds and it's cold outside, I have a hard time keeping my feet warm. TXVue04 did a test where she held a ribbon near the speaker grille at highway speeds, with the vent closed, windows closed, and the air seeping in was enough to blow the ribbon out from the speaker grille. That's a lot of outside air to be leaking in...

Consider, also, when you put your knob at floor or anything towards defrost past that, that it ALSO automatically opens the vents for outside air, i.e. turns off recirculate... So, when it's cold and you want to keep the warm, dry air inside the car, it AUTOMATICALLY opens the vents to let the cold, humid air in, where it then has to HEAT AND DRY it, both of which require energy (and therefore cost you in fuel). Trust me, no NASA engineer designed this system. I think a monkey did. It's completely idiotic, and assumes YOU, the owner are as stupid. You should be able to override its "suggested" settings by turning OFF the damn A/C compressor and closing the damn vents when it's 39 degrees and raining outside so that the air that you have already heated and dried will stay in, and the cold and humid air will stay out... but instead, the system forces the cold, humid air in and YOU have no say in it.

You can't override the vent, so you might as well leave the a/c compressor relay in, otherwise you may get condensation issues. If all else fails, suffer through it, put the vent position 1 click before floor and point the vents down so you don't get a blast of hot air in the face.

The HVAC system in the Vue is RIDICULOUSLY stupid. My uber-low-tech Toyota worked so much better. 5 fan speeds (off, 1-4), a sliding heat scale from cold to warm, a BUTTON to engage the A/C, and a sliding switch for the vent. Simple, classic, has worked for 80 years, WHY GO AND SCREW IT UP, SATURN???? Stupid crap... :x < / rant >

[99blacktop]

I just took my VUE out to grab lunch, it was about 46 degrees and raining. Rain-X doesn't work too well at low speeds, so I was forced to use my wipers. At 46 degrees, the wiper blades are pretty stiff, so they pretty much just skip across the window. I put the vent on defrost to warm up the windshield/wipers and after a couple minutes, problem solved.

Since the outside temperature was above the threshold, the a/c compressor kicked on. Yes, it was cold and rainy, but there was zero "fog" on the inside of the windows, even though I had it on bi-level prior to that and was blowing warm air on my damp floormats.

Yet another reason I wish I had the control. :x Maybe I can rip the HVAC out of Dante's old Toyota. :D

[99blacktop]

Duplicate :rolleyes:

[vue-vtec]

......Also note the compressor description. The compressor being a variable displacement compressor will under low load conditons, think low ambient temps, not take much power to run......


Probably takes next to nothing to run it.

Auto makers are doing everything they can to get the CAFE numbers up. Do you really think their engineers are complete idiots and have designed a HVAC system made to waste fuel?