SaturnFans.com
saturnfans.com - classifieds - forums - webmail


Go Back   SaturnFans.com Forums > Models > Saturn S-Series > S-Series Tech

Reply
 
Thread Tools Display Modes
Old 01-07-2008, 11:07 PM   #1
npdimonte
Member
npdimonte will become famous soon enoughnpdimonte will become famous soon enough
 
Join Date: Feb 2004
Posts: 70
Question A/C not working below 40 degrees

While troubleshooting a code 32 problem in 30 degree weather, I noticed that my A/C would not engage. My service manual states that the ECM will cycle the A/C once every 90 seconds when the ambient temperature is between 40-60 degrees. The manual however doesn't mention what happens when the temperature is below 40 degrees. I have searched the forum and found that others have indicated that the A/C will not engage below 40 degrees. But why?

All my other cars I have owned always worked below 40 degrees. Why doesn't my '93 SL2 work below 40? When the temp is in the 30's, it can be a pain to keep the windows clear.

Nick
'93 SL2
npdimonte is offline   Reply With Quote
SaturnFans.com Sponsored Links
Old 01-08-2008, 12:17 AM   #2
fdryer
Super Member
fdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond repute
 
fdryer's Avatar
 
Join Date: Jan 2006
Location: NYC
Posts: 44,021
 

2003 L-Series 3.0L Sedan
Default Re: A/C not working below 40 degrees

Your answer is in the HVAC chapter. In there will be a description of the low/high pressure switch that prevents a/c compressor operation from; excessive refrigerant inadvertently added incorrectly, too little refrigerant (from a leak or undercharging of refrigerant), or ambient (outside) temperatures of approximately 40F. that would lower the internal refrigerant pressure below the threshold, automatically disabling the compressor clutch circuit. A low charge (leak) or low outside temperature is the same pressure detected by the combination low/high pressure switch. If you really need more information than this then I would suggest you review some physics/chemistry laws; Charle's Law and Boyle's Law governing temperature/pressure relationships in a closed volume as well as a variable volume. The majority of us don't want a/c use below 40F. since its already cold enough to let in outside air into the car interior but there will be exceptions like you, wanting a/c air for defrost use. Unfortunately, the low/high pressure switch is fixed and the only work-around to this, and should be very carefully considered, is to pull the pressure switch connector and put a paper clip into the connector. This will now allow you to run the a/c in the low temperatures but you will need to know and understand the risks of running w/o the pressure switch.

1-If the a/c system is low on refrigerant and you use it this way, there is a very good possibility of damaging the compressor by running it without the benefit of refrigerant oil to lubricate the moving parts within the compressor. R12 or R134a is used to move the lubricating oil throughout the a/c system to eventually wind up back in the compressor to lubricate it. Little to no R12/R134a is the same as running the compressor dry, no lubricating oil, quickly destroying the compressor. An expensive risk.

2-The normal outlet temperatures of a running a/c system is always above freezing temps, 40F. approximately, and a low amount of refrigerant promotes freezing temperatures at the evaporator coils that quickly freezes moisture in the air coating the coils in ice forming an ice block. The pressure switch prevents this from occurring by detecting the low pressure and opens the clutch circuit preventing the evaporator coils from freezing. A normal refrigerant charge will never approach the freezing temps as long as the system remains sealed. If the pressure switch is bypassed and there's a normal amount of refrigerant in the system and the a/c is used in temps below 40F. there is a small chance that this can work but a very small chance as there's no protection if a leak occurs and isn't detected by the pressure switch that's no longer used - compressor damage. Worth the risk? There's more shock and vibration in the cold weather from frozen snow that transmits into the a/c system plumbing to induce stress cracks in the fragile aliminum lines and fittings.

Most of us just turn the heat up to the max to help defrost the windows and the interior. There are the few instances where moisture is heavy in near freezing temperatures but for the most part the heater on maximum will slowly dry out interior moisture accumulation as long as the recirculation mode isn't selected. As old as your car is, there a better than average chance that your a/c system will or already leak out refrigerant. You assume all risks and damage to your a/c system if you cannot verify that your a/c system is completely intact and running as if it came off the assembly line, in order to bypass the pressure switch.
...
VCX NANO
fdryer is online now   Reply With Quote
Old 01-08-2008, 12:24 AM   #3
97coupe
Master Member
97coupe is on a distinguished road
 
Join Date: Jun 2006
Posts: 2,260

1997 SC2
Default Re: A/C not working below 40 degrees

There is a low pressure cutout switch in A/C system and as temp drops so does static pressure of refrigerant. R134 can exist as a liquid at minus 15F at standard pressure and at 30F it is about 35 PSI. IF it is allowed to operated at to low a temp and pressure the evaporator can freeze solid and liquid could possible be ingested by compressor and it would be damaged so operation is blocked. Too low a static pressure at higher temps due to a low charge can cause the compressor to not be properly cooled and lube so low pressure switch serves two safeguarding functions.
97coupe is offline   Reply With Quote
Old 01-08-2008, 10:16 AM   #4
npdimonte
Member
npdimonte will become famous soon enoughnpdimonte will become famous soon enough
 
Join Date: Feb 2004
Posts: 70
Default Re: A/C not working below 40 degrees

Thanks for the detailed replies. I forgot to mention that I did a 134a conversion several years ago, which is still producing good A/C. I'm not sure why someone would not want A/C on when trying to defog your windows. I can defog my windows without A/C if I'm by myself, but it will just take a little longer. But why wait? The problem gets worse when more people are in the car as in my case. When my family of four is in the car, the fog issue is really difficult to clear when the A/C is off.

Like I have said before, my other cars work all the time. My Mercury Villager's A/C works at any temp that I have used it in. It really makes a big difference when the A/C is off. To me its a safety issues to be able to see clearly. I like my Saturn, its been very good to me with 180k, but I'm disappointed that the A/C doesn't work below 40 degrees.

Again, thanks for the detailed explanation on how the A/C system functions.
Nick
npdimonte is offline   Reply With Quote
Old 01-08-2008, 11:01 AM   #5
fdryer
Super Member
fdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond repute
 
fdryer's Avatar
 
Join Date: Jan 2006
Location: NYC
Posts: 44,021
 

2003 L-Series 3.0L Sedan
Default Re: A/C not working below 40 degrees

I was afraid you were going to bring up the fact that more people in the car makes defogging more difficult and agree with you completely. I've had similar experiences as well and am sure there are others in the same situation. My guess is to find the magic combination of outside/heater air and re-directing it several times, tedious but you get the point.
...
VCX NANO
fdryer is online now   Reply With Quote
Old 01-08-2008, 12:39 PM   #6
compo1
Junior Member
compo1 is on a distinguished road
 
Join Date: Sep 2006
Posts: 23
Default Re: A/C not working below 40 degrees

just out of curiousity,why, as he mentioned, do other cars such as his mercury milan and my 97 honda civic ac come on automatically when you press the defrost button...it seems the same risks would apply to these systems,or do they have a built-in safeguard...seems contradictory,but i'm sure there is a reason
compo1 is offline   Reply With Quote
Old 01-08-2008, 01:13 PM   #7
fdryer
Super Member
fdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond repute
 
fdryer's Avatar
 
Join Date: Jan 2006
Location: NYC
Posts: 44,021
 

2003 L-Series 3.0L Sedan
Default Re: A/C not working below 40 degrees

As I don't have factual information for the other car makers, and a/c is a/c, it doesn't matter which vehicle has it so it can be presumed that certain guidelines safeguard the a/c from damage, including low temperature shutoff when ambient temperatures are low enough to adversely affect normal a/c operation. Looking at it another way, who runs their home air conditioner in the winter if their windows fog up or condensation builds up on the windows?
...
VCX NANO
fdryer is online now   Reply With Quote
Old 01-08-2008, 01:18 PM   #8
npdimonte
Member
npdimonte will become famous soon enoughnpdimonte will become famous soon enough
 
Join Date: Feb 2004
Posts: 70
Default Re: A/C not working below 40 degrees

Quote:
Originally Posted by compo1 View Post
just out of curiousity,why, as he mentioned, do other cars such as his mercury milan and my 97 honda civic ac come on automatically when you press the defrost button...it seems the same risks would apply to these systems,or do they have a built-in safeguard...seems contradictory,but i'm sure there is a reason
I'm not the expert when it comes to A/C systems, which is why I posted my question. I have always been able to have the A/C come on no matter what the temp was, but maybe I just never noticed the safe guards working on my other vehicles. The important thing for me is that I have a better understanding on how my A/C system works on my Saturn, thanks to this forum, which will help me to utilize my system to its fullest.

Thanks again,
Nick
npdimonte is offline   Reply With Quote
Old 01-08-2008, 01:53 PM   #9
97coupe
Master Member
97coupe is on a distinguished road
 
Join Date: Jun 2006
Posts: 2,260

1997 SC2
Default Re: A/C not working below 40 degrees

Quote:
Originally Posted by fdryer View Post
Looking at it another way, who runs their home air conditioner in the winter if their windows fog up or condensation builds up on the windows?

Well on your home A/C does not have the ability to run heat and cool at same time and also if you could it would waste a lot of energy. Furthermore, home A/C's have variable temp controlled expansion valves to control flow through evaporators which were removed from cars in 70's and replaced with a cheaper fixed orifice design mandating the usage of a cut out switch to prevent problems. (R134 also saw the addition of a high pressure cutout switch because pressure with R134 climb faster with temp than R12 does and can get dangerously high under the right conditions without this cut out switch. Most GM low pressure cut out switches are adjustable so you could tweak it a bit to operate at a lower temp.
97coupe is offline   Reply With Quote
Old 01-08-2008, 02:10 PM   #10
Bruce Rock
Member
Bruce Rock is a jewel in the roughBruce Rock is a jewel in the roughBruce Rock is a jewel in the roughBruce Rock is a jewel in the rough
 
Join Date: Sep 2007
Location: Kaukauna, WI
Posts: 297

2000 SL2
2006 VUE 2.2L
Default Re: A/C not working below 40 degrees

I've got a '98 Villager. The cycling switch prevents the compressor form operating below about 48 degrees F

From the Factory Service CD:


The electrical A/C cycling switch contacts will open when the suction pressure is approximately 169 kPa (24.5 psi). They will close when the suction pressure rises to approximately 276-324 kPa (40-47 psi) or above. Ambient temperatures that are below approximately 9C (48F) will prevent the suction pressure from closing the A/C cycling switch contacts.
Bruce Rock is offline   Reply With Quote
Old 01-08-2008, 03:45 PM   #11
npdimonte
Member
npdimonte will become famous soon enoughnpdimonte will become famous soon enough
 
Join Date: Feb 2004
Posts: 70
Default Re: A/C not working below 40 degrees

Quote:
Originally Posted by Bruce Rock View Post
I've got a '98 Villager. The cycling switch prevents the compressor form operating below about 48 degrees F

From the Factory Service CD:


The electrical A/C cycling switch contacts will open when the suction pressure is approximately 169 kPa (24.5 psi). They will close when the suction pressure rises to approximately 276-324 kPa (40-47 psi) or above. Ambient temperatures that are below approximately 9C (48F) will prevent the suction pressure from closing the A/C cycling switch contacts.
My Villager is a '97 and without question the A/C works below 48 degF. I would like to know if your manual covers my year. I would be very interested in knowing what it says.

Darn it. Now I'm gonna test this out tonight, to make sure I'm not losing it.

Because my Olds, Chevy, Pontiac's and Buick (total 7) through the 70's, 80's and 90's automatically turned on the A/C when the defroster was selected. My Villager has the automatic climate control system which engages the A/C when set to AUTO mode. I'm always telling my 17yr old to use the manual heater mode to save on gas. But, tonight I'll verify its operation. Here in Chicago its currently 51 degF but should drop down to around 28 degF tonight. I'll let you know.
npdimonte is offline   Reply With Quote
Old 01-08-2008, 03:56 PM   #12
97coupe
Master Member
97coupe is on a distinguished road
 
Join Date: Jun 2006
Posts: 2,260

1997 SC2
Default Re: A/C not working below 40 degrees

The A/C on my GM truck works well down into 30's on defrost. So does my daughters 97 SC2.
97coupe is offline   Reply With Quote
Old 01-08-2008, 04:23 PM   #13
madpogue
Super Member
madpogue has much to be proud ofmadpogue has much to be proud ofmadpogue has much to be proud ofmadpogue has much to be proud ofmadpogue has much to be proud ofmadpogue has much to be proud ofmadpogue has much to be proud ofmadpogue has much to be proud of
 
Join Date: Sep 2004
Location: Madison, WI USA
Posts: 25,715
 

1996 SW2
Default Re: A/C not working below 40 degrees

Another "elephant in the corner" question. How does it know the outside temperature? I doubt it maintains a wireless Internet link to NOAA. My WAG (wild-@ss guess) is that it uses the IAT sensor temperature. But of course, even on a sub-40F day, that air can get warmer than 40F when you've been driving a while, so I can see how some folks' A/C would work in such situations. 'Course, that's not much help, in that you REALLY need the dry-air defog at launch.
madpogue is offline   Reply With Quote
Old 01-08-2008, 05:20 PM   #14
topcat
Member
topcat will become famous soon enough
 
topcat's Avatar
 
Join Date: Jun 2005
Location: boston,ma
Posts: 456

2005 VUE 3.5L
Default Re: A/C not working below 40 degrees

Just a function of the hi-low pressure switch. From high school physics:

The relationship between gas volume (V), pressure (P), and temperature (T) can be expressed by the ideal gas law:

PV/T= constant

where P = pressure of gas, V = volume occupied, and T = temperature.

In simpler terms, if volume is constant, an increase in temperature results in a proportional increase in pressure. If pressure is constant, an increase in temperature results in a proportional increase in volume. Inversely, if volume is decreased and pressure remains constant, temperature must decrease. Basically, pressure and volume are directly proportional to temperature and inversely proportional to each other.
topcat is offline   Reply With Quote
Old 01-08-2008, 05:24 PM   #15
97coupe
Master Member
97coupe is on a distinguished road
 
Join Date: Jun 2006
Posts: 2,260

1997 SC2
Default Re: A/C not working below 40 degrees

Quote:
Originally Posted by madpogue View Post
Another "elephant in the corner" question. How does it know the outside temperature? I doubt it maintains a wireless Internet link to NOAA. My WAG (wild-@ss guess) is that it uses the IAT sensor temperature. But of course, even on a sub-40F day, that air can get warmer than 40F when you've been driving a while, so I can see how some folks' A/C would work in such situations. 'Course, that's not much help, in that you REALLY need the dry-air defog at launch.

The answer is it does not give hoot what temperature is. It works off system pressure. When it is cold outside but warm under hood is can raise system temperature/pressure to point it will run. So i guess you can say that temp has effect but only as far as system static pressure not free air temp via a sensor.
97coupe is offline   Reply With Quote
Old 01-09-2008, 02:39 AM   #16
Bruce Rock
Member
Bruce Rock is a jewel in the roughBruce Rock is a jewel in the roughBruce Rock is a jewel in the roughBruce Rock is a jewel in the rough
 
Join Date: Sep 2007
Location: Kaukauna, WI
Posts: 297

2000 SL2
2006 VUE 2.2L
Default Re: A/C not working below 40 degrees

Sorry, my factory CD doesn't cover the '97 Villager.

I had to do some A/C work on our '94 Explorer (replaced the rusted out accumulator/dryer to which the cycle switch is mounted - Why Ford would choose to use steel when everyone else makes theirs out of AL makes me wonder) so I know it's the same way.

I know the cycle switch on the explorer is adjustable and I believe the Villager uses the same one.

Provided you don't have any air or moisture in your system you can determine the pressure in the system from the temperature and this chart:

http://www.csgnetwork.com/r134apresstempconv.html

One more thing. I also have a '93 Saturn. I've driven it less than 150 miles. One night I had problems with the windows fogging up. Found out the problem was I had the recirculation mode on. It's a separate switch on the Saturn, on the right side of the heater control panel. First car I've seen or heard of that does it like that. On the cars I've had, the recirculation mode is only available by selecting MAX AIR (airconditioning mode)

Hope this clears things up for you
Bruce Rock is offline   Reply With Quote
Old 01-09-2008, 02:50 AM   #17
SaturnManiac
Master Member
SaturnManiac is on a distinguished road
 
SaturnManiac's Avatar
 
Join Date: Feb 2006
Location: Near VA Border
Posts: 3,648
 
Default Re: A/C not working below 40 degrees

It's not going to work at too low of temps as others have stated...safety feature. The system could freeze up and get damaged, basically.
...
R.I.P. - My 1996 Saturn SL2, "Psycho" - 7/95-2/17/06

R.I.P. - My 2000 Saturn SL2, "Sexy" - 11/24/99-8/05/08

If you're a car begging for your life, wouldn't you want someone to add fluids?
SaturnManiac is offline   Reply With Quote
Old 01-09-2008, 09:52 AM   #18
npdimonte
Member
npdimonte will become famous soon enoughnpdimonte will become famous soon enough
 
Join Date: Feb 2004
Posts: 70
Default Re: A/C not working below 40 degrees

Quote:
Originally Posted by Bruce Rock View Post
Sorry, my factory CD doesn't cover the '97 Villager.

I had to do some A/C work on our '94 Explorer (replaced the rusted out accumulator/dryer to which the cycle switch is mounted - Why Ford would choose to use steel when everyone else makes theirs out of AL makes me wonder) so I know it's the same way.

I know the cycle switch on the explorer is adjustable and I believe the Villager uses the same one.

Provided you don't have any air or moisture in your system you can determine the pressure in the system from the temperature and this chart:

http://www.csgnetwork.com/r134apresstempconv.html

One more thing. I also have a '93 Saturn. I've driven it less than 150 miles. One night I had problems with the windows fogging up. Found out the problem was I had the recirculation mode on. It's a separate switch on the Saturn, on the right side of the heater control panel. First car I've seen or heard of that does it like that. On the cars I've had, the recirculation mode is only available by selecting MAX AIR (airconditioning mode)

Hope this clears things up for you
Thanks Bruce for the "cool" web site. I'll try to put it to good use this weekend.

As for my test, last night the temp only got down to 37 degF around Chicago. Crazy weather! But both the Saturn and Villager's A/C turn on. However, this morning the temp drop to 33 degF and only the Villager's A/C would turn on. I will test the system to determine if its the low pressure switch or if the ECM thinks its too cold to run.

About the recirculation mode switch, both Villager and my Saturn have this switch, otherwise my experience is like yours with the "MAX AIR" mode.

Here's a question, could this condition indicate the system is low on R134a? Did the original R12 work in like manner?
npdimonte is offline   Reply With Quote
Old 01-09-2008, 10:18 AM   #19
97coupe
Master Member
97coupe is on a distinguished road
 
Join Date: Jun 2006
Posts: 2,260

1997 SC2
Default Re: A/C not working below 40 degrees

The ECM does not care at all about this. It is strictly static system pressure and low pressure cut out switch. Like I said earlier, you should be able to adjust switch. Each full turn clockwise of screw on switch between contact blades under connector lowers cut out pressure about 3 PSI and therefore lowers operating temp too.
97coupe is offline   Reply With Quote
Old 01-09-2008, 10:56 AM   #20
fdryer
Super Member
fdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond reputefdryer has a reputation beyond repute
 
fdryer's Avatar
 
Join Date: Jan 2006
Location: NYC
Posts: 44,021
 

2003 L-Series 3.0L Sedan
Default Re: A/C not working below 40 degrees

Quote:
Originally Posted by npdimonte View Post
Here's a question, could this condition indicate the system is low on R134a? Did the original R12 work in like manner?
In one word, yes. The ECM/PCM has nothing to do with the a/c system as it is soley an engine control computer. The a/c system would run by itself, in manual mode or in auto climate control mode with its own temperature sensing system to monitor interior temps for regulating the a/c and heat simultaneously, mixing the two as necessary to achieve temperature stability just like at home but with the a little more complexity as two independent systems are running, the heater and the a/c. In manual mode you are moving a blend door to allow heat and a/c to mix simultaneously to get the desired cooling/heating/defrosting. The a/c low/high pressure switch is for monitoring dangerous pressures that would harm the compressor if this sealed system becomes compromised.
...
VCX NANO
fdryer is online now   Reply With Quote
Reply

Bookmarks


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
100 degrees SES Light! redkees@msn.com S-Series Tech 7 06-28-2007 01:24 PM
old intake idea 7-9 degrees cooler tarsun S-Series Mods 2 03-25-2007 11:12 AM
5F degrees outside. Car wont start. DiabloDan S-Series General 12 01-24-2007 03:33 PM
Vti at -25 degrees corympak Vue General 6 02-15-2003 02:07 PM
This is how I get 15 degrees cooler air Son93SL2 General Saturn Discussion 0 06-04-2001 08:42 PM


All times are GMT -4. The time now is 06:35 PM.

Advanced Forum Search | Advanced Photo Search


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
SaturnFans.com. The Saturn Enthusiasts Site.