A/C in a 99 Vette
Pro
Joined: Oct 2009
Posts: 560
Likes: 3
From: Centennial Colorado
QCVette, Quicksilver Vert 01, Bill, and txst...
Thank YOU! Finally what I wanted to hear…an actual technical description of the problem and operation. As a retired Navy aircraft electrician, I could not accept the "…it worked for me…" responses without knowing why. Just couldn't risk people's lives fixing an airplane with that answer. Had to be right, and I had to know why it was right.
Now I do.
I can see now why low levels would cause the driver's side to be warm in the scenario presented, but my situation is the opposite… cold on the driver's side, hot on the passenger side. And, I do have the codes that won't reset for the right side actuator. I'm very confident that replacing it will solve my issue. Once again, thanks for the great information.
I'd like to hear if the OP has any related codes?
Thank YOU! Finally what I wanted to hear…an actual technical description of the problem and operation. As a retired Navy aircraft electrician, I could not accept the "…it worked for me…" responses without knowing why. Just couldn't risk people's lives fixing an airplane with that answer. Had to be right, and I had to know why it was right.
Now I do.
I can see now why low levels would cause the driver's side to be warm in the scenario presented, but my situation is the opposite… cold on the driver's side, hot on the passenger side. And, I do have the codes that won't reset for the right side actuator. I'm very confident that replacing it will solve my issue. Once again, thanks for the great information.
I'd like to hear if the OP has any related codes?
Racer
Joined: Jan 2010
Posts: 261
Likes: 6
From: Alva Oklahoma
Instructor
Joined: Feb 2006
Posts: 143
Likes: 4
From: Wichita KS
No problem.
As long as people are interested, I can further explain with thermodynamics why a low refrigerant charge can change the balance of capacity between the passenger's side and the driver's side:
Our dual zone systems have what is described as a "face split evaporator", where a single expansion device (the orifice) feeds 2 separate circuits in the evaporator. It is difficult to balance the flow of refrigerant equally in this type of design, even under ideal conditions. The balance depends on proper charge, proper airflow, etc. If the amount of refrigerant is not in the design parameters, the refrigerant flow become non-uniform. When this happens, one side can become starved with refrigerant, and becomes warmer. When it becomes warmer, it does not form any condensate, and the airflow pressure drop is less in that area (no water on the cooling fins to block the air). This causes more air volume from the blower motor to go through the warmer section with less air side pressure drop, and less volume of air flows over the colder section of the evaporator (making it colder), and the internal pressure in the warmer portion of the evaporator becomes slightly higher than the pressure in the colder section of the evoporator, and draws even more refrigerant into the colder section, thus making the problem even worse. Thus, the colder section of the evaporator has reduced capacity because it's low on refrigerant, but it's getting less air, so the temperature of that section does not get radically warmer (in the neighborhood of 15+ degrees, depending on how low the refrigerant level is), but it's capacity is substantially reduced.
As I said before, a low refrigerant charge level will cause reduced capacity, as will a leaky damper which allows air from the heater core to enter the system. If your system is low on refrigerant, you should not get cold air from one side, but you may get cool air (depending on how low the level is). If you had a leaky damper door, you may get cold air on one side and cool air on the other (depending on how much air is leaking). If you get air out of a vent that is above the cabin air temperature with the A/C on and the system on recirculate, you most likely have a damper problem, as it is physically and thermodynamically impossible for a starved evaporator to generate heat - it just won't remove any.
The A/C system in a car is amazing. It has variable capacity (from the various RPMS of the engine/compressor), it has variable airflow (multiple fan speed settings), has wild swings in evaporator inlet air temperatures (your home/office A/C system never has return air temperatures in the 120+ degree range) and it has a fairly low refrigerant charge level which makes the performance extremely sensitive. It's incredible that the things work as well as they do.
Thus ends your lesson in HVAC 101.
As long as people are interested, I can further explain with thermodynamics why a low refrigerant charge can change the balance of capacity between the passenger's side and the driver's side:
Our dual zone systems have what is described as a "face split evaporator", where a single expansion device (the orifice) feeds 2 separate circuits in the evaporator. It is difficult to balance the flow of refrigerant equally in this type of design, even under ideal conditions. The balance depends on proper charge, proper airflow, etc. If the amount of refrigerant is not in the design parameters, the refrigerant flow become non-uniform. When this happens, one side can become starved with refrigerant, and becomes warmer. When it becomes warmer, it does not form any condensate, and the airflow pressure drop is less in that area (no water on the cooling fins to block the air). This causes more air volume from the blower motor to go through the warmer section with less air side pressure drop, and less volume of air flows over the colder section of the evaporator (making it colder), and the internal pressure in the warmer portion of the evaporator becomes slightly higher than the pressure in the colder section of the evoporator, and draws even more refrigerant into the colder section, thus making the problem even worse. Thus, the colder section of the evaporator has reduced capacity because it's low on refrigerant, but it's getting less air, so the temperature of that section does not get radically warmer (in the neighborhood of 15+ degrees, depending on how low the refrigerant level is), but it's capacity is substantially reduced.
As I said before, a low refrigerant charge level will cause reduced capacity, as will a leaky damper which allows air from the heater core to enter the system. If your system is low on refrigerant, you should not get cold air from one side, but you may get cool air (depending on how low the level is). If you had a leaky damper door, you may get cold air on one side and cool air on the other (depending on how much air is leaking). If you get air out of a vent that is above the cabin air temperature with the A/C on and the system on recirculate, you most likely have a damper problem, as it is physically and thermodynamically impossible for a starved evaporator to generate heat - it just won't remove any.
The A/C system in a car is amazing. It has variable capacity (from the various RPMS of the engine/compressor), it has variable airflow (multiple fan speed settings), has wild swings in evaporator inlet air temperatures (your home/office A/C system never has return air temperatures in the 120+ degree range) and it has a fairly low refrigerant charge level which makes the performance extremely sensitive. It's incredible that the things work as well as they do.
Thus ends your lesson in HVAC 101.
Tech Contributor
Joined: May 2008
Posts: 3,100
Likes: 17
From: Somers, CT and Clermont, FL
St. Jude Donor '09-'10-'11-'12-'13-'14-'15-'16
Le Mans Master
Joined: Jan 2001
Posts: 5,015
Likes: 508
From: Hilton NY
Txst; I read about black death of compressors where metal particles from compressor wear combine with the old refrigerant oil and plug up the screen filter then the compressor blows up adding junk throughout the system. The owner adding cans of various products from year to year didn't help the situation either. It was recommended to flush out the system, change the receiver dryer, screen filter and add the correct amount of oil at 60,000 miles to avoid this. The AC in my car is working at 107,000 miles so should it be left alone or is it due for some work? What do you recommend for high mileage C5's?
Instructor
Joined: Feb 2006
Posts: 143
Likes: 4
From: Wichita KS
Txst; I read about black death of compressors where metal particles from compressor wear combine with the old refrigerant oil and plug up the screen filter then the compressor blows up adding junk throughout the system. The owner adding cans of various products from year to year didn't help the situation either. It was recommended to flush out the system, change the receiver dryer, screen filter and add the correct amount of oil at 60,000 miles to avoid this. The AC in my car is working at 107,000 miles so should it be left alone or is it due for some work? What do you recommend for high mileage C5's?
Since it is so hard to find someone who knows what they are doing, anytime you open the refrigeration system, you risk all kinds of things going wrong, especially moisture getting in the system from the air (which turns to acid in a refrigeration system). Unless you draw a good vaccum and boil out all of the moisture after everything is put back together and there is a sufficient level of oil in the system, you purge the air out of the charging hoses, and you get it charged to the correct level, you will cause more damage than it is worth. My recomendation is if it ain't broke - don't fix it. If it is not blowing cold air, run away from anyone who doesn't use a proper gauge set with 2 hoses to diagnose it, and anyone who want's to charge it with a single hose connected to the suction line - It is almost impossible to get it right.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
No problem.
As long as people are interested, I can further explain with thermodynamics why a low refrigerant charge can change the balance of capacity between the passenger's side and the driver's side:
Our dual zone systems have what is described as a "face split evaporator", where a single expansion device (the orifice) feeds 2 separate circuits in the evaporator. It is difficult to balance the flow of refrigerant equally in this type of design, even under ideal conditions. The balance depends on proper charge, proper airflow, etc. If the amount of refrigerant is not in the design parameters, the refrigerant flow become non-uniform. When this happens, one side can become starved with refrigerant, and becomes warmer. When it becomes warmer, it does not form any condensate, and the airflow pressure drop is less in that area (no water on the cooling fins to block the air). This causes more air volume from the blower motor to go through the warmer section with less air side pressure drop, and less volume of air flows over the colder section of the evaporator (making it colder), and the internal pressure in the warmer portion of the evaporator becomes slightly higher than the pressure in the colder section of the evoporator, and draws even more refrigerant into the colder section, thus making the problem even worse. Thus, the colder section of the evaporator has reduced capacity because it's low on refrigerant, but it's getting less air, so the temperature of that section does not get radically warmer (in the neighborhood of 15+ degrees, depending on how low the refrigerant level is), but it's capacity is substantially reduced.
As I said before, a low refrigerant charge level will cause reduced capacity, as will a leaky damper which allows air from the heater core to enter the system. If your system is low on refrigerant, you should not get cold air from one side, but you may get cool air (depending on how low the level is). If you had a leaky damper door, you may get cold air on one side and cool air on the other (depending on how much air is leaking). If you get air out of a vent that is above the cabin air temperature with the A/C on and the system on recirculate, you most likely have a damper problem, as it is physically and thermodynamically impossible for a starved evaporator to generate heat - it just won't remove any.
The A/C system in a car is amazing. It has variable capacity (from the various RPMS of the engine/compressor), it has variable airflow (multiple fan speed settings), has wild swings in evaporator inlet air temperatures (your home/office A/C system never has return air temperatures in the 120+ degree range) and it has a fairly low refrigerant charge level which makes the performance extremely sensitive. It's incredible that the things work as well as they do.
Thus ends your lesson in HVAC 101.
As long as people are interested, I can further explain with thermodynamics why a low refrigerant charge can change the balance of capacity between the passenger's side and the driver's side:
Our dual zone systems have what is described as a "face split evaporator", where a single expansion device (the orifice) feeds 2 separate circuits in the evaporator. It is difficult to balance the flow of refrigerant equally in this type of design, even under ideal conditions. The balance depends on proper charge, proper airflow, etc. If the amount of refrigerant is not in the design parameters, the refrigerant flow become non-uniform. When this happens, one side can become starved with refrigerant, and becomes warmer. When it becomes warmer, it does not form any condensate, and the airflow pressure drop is less in that area (no water on the cooling fins to block the air). This causes more air volume from the blower motor to go through the warmer section with less air side pressure drop, and less volume of air flows over the colder section of the evaporator (making it colder), and the internal pressure in the warmer portion of the evaporator becomes slightly higher than the pressure in the colder section of the evoporator, and draws even more refrigerant into the colder section, thus making the problem even worse. Thus, the colder section of the evaporator has reduced capacity because it's low on refrigerant, but it's getting less air, so the temperature of that section does not get radically warmer (in the neighborhood of 15+ degrees, depending on how low the refrigerant level is), but it's capacity is substantially reduced.
As I said before, a low refrigerant charge level will cause reduced capacity, as will a leaky damper which allows air from the heater core to enter the system. If your system is low on refrigerant, you should not get cold air from one side, but you may get cool air (depending on how low the level is). If you had a leaky damper door, you may get cold air on one side and cool air on the other (depending on how much air is leaking). If you get air out of a vent that is above the cabin air temperature with the A/C on and the system on recirculate, you most likely have a damper problem, as it is physically and thermodynamically impossible for a starved evaporator to generate heat - it just won't remove any.
The A/C system in a car is amazing. It has variable capacity (from the various RPMS of the engine/compressor), it has variable airflow (multiple fan speed settings), has wild swings in evaporator inlet air temperatures (your home/office A/C system never has return air temperatures in the 120+ degree range) and it has a fairly low refrigerant charge level which makes the performance extremely sensitive. It's incredible that the things work as well as they do.
Thus ends your lesson in HVAC 101.
TXST
YOU MY FRIEND,,,, are now crowned "THE HVAC AC GO TO DUDE!"
WOW!
EXCELLENT INFO!
Im self taught and do all my own AC WORK. Did a LOT
of research on auto AC Systems because I use to be POOR and couldn’t afford to have people fix my AC Systems. Got all my AC tools and equipment used and learned how to use it. I have a massive vacuum pump that will suck a golf ball thru a garden hose!!!
Its a high volume pump that was used to service metro rail AC SYSTEMS.
The C5/C6 Service Manual has a massive chapter on ALL the AC SYSTEM INFO! If you don’t follow it,, just EMPTY YOUR WALLET at the parts counter and tell them to take what they need!
It contains some VERY specific and detailed info. Especially the charts for efficiency and charging pressures!
Its excellent to know that there’s someone that has excellent AC knowledge on the forum! IM SIGNIFICANTLY IMPRESSED!
You should see some of the AC Habitability systems on the new submarines!
Bill
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Burning Brakes
Joined: Oct 2004
Posts: 925
Likes: 4
From: EXTON PA
Well,,,,,,,,,,,,, you have to examine how our HVAC system with DUAL ZONE works. The heat coils are always the temp of the coolant. You have a DAMPER DOOR for the drivers side and a DAMPER DOOR for the passengers side.
The damper door allows the air from the fan to either flow thru the heat coil or the AC COIL or a mixture of both.
Your damper doors MUST be fully functional to allow the system to work properly
Like it was recommended previously.. check your DTCs in the DIC and see if you have any HVAC codes. Especially the ones for the actuators.
If you have HVAC DTC for the actuators, it can and will fail during the cycle period and if it fails in the heat position,,,, you get heat
Try this:
Turn the HVAC OFF. Clear the DTCs and listen for the actuators to cycle. If they don't cycle, turn the HVAC ON and see if they cycle. Look in the DIC and see if the actuators error out and set a DTC.
I had to clear the DTCS on mine a bunch of times before it worked normal and stopped throwing DTCs.
LOW R-134
Remember,,,, Our cooling coils are sort of divided in to TWO separate coils. It is possible to be low enough for the orifice tube to spray freon enough to cool only half of the coils before it flashes off and can no longer remove any heat. from the other coil further down the line.
So,,, If your actuators are working properly and have FULL range and you have heat on one side,, it has to be a low R-134 issue
IF you look on the side of an actuator you can see the output shaft collar and watch it move when you adjust it
Sometimes the output-drive shaft gear cracks and causes the actuator to deliver the incorrect air temp of set a DTCs during the cycle portion of the self test when the head is turned on of the DTCs are cleared.
The passengers side actuator will follow the drivers actuator and the passengers **** will vary the damper +- 10% of the drivers set temp. That prevents thunder storms between the drivers side and the passengers side!
The damper door allows the air from the fan to either flow thru the heat coil or the AC COIL or a mixture of both.
Your damper doors MUST be fully functional to allow the system to work properly
Like it was recommended previously.. check your DTCs in the DIC and see if you have any HVAC codes. Especially the ones for the actuators.
If you have HVAC DTC for the actuators, it can and will fail during the cycle period and if it fails in the heat position,,,, you get heat
Try this:
Turn the HVAC OFF. Clear the DTCs and listen for the actuators to cycle. If they don't cycle, turn the HVAC ON and see if they cycle. Look in the DIC and see if the actuators error out and set a DTC.
I had to clear the DTCS on mine a bunch of times before it worked normal and stopped throwing DTCs.
LOW R-134
Remember,,,, Our cooling coils are sort of divided in to TWO separate coils. It is possible to be low enough for the orifice tube to spray freon enough to cool only half of the coils before it flashes off and can no longer remove any heat. from the other coil further down the line.
So,,, If your actuators are working properly and have FULL range and you have heat on one side,, it has to be a low R-134 issue
IF you look on the side of an actuator you can see the output shaft collar and watch it move when you adjust it
Sometimes the output-drive shaft gear cracks and causes the actuator to deliver the incorrect air temp of set a DTCs during the cycle portion of the self test when the head is turned on of the DTCs are cleared.
The passengers side actuator will follow the drivers actuator and the passengers **** will vary the damper +- 10% of the drivers set temp. That prevents thunder storms between the drivers side and the passengers side!
What a great resoure of Information with great visual attachments..Thank You
Thread Starter
Racer
Joined: Sep 2000
Posts: 412
Likes: 34
From: Blairsville....North Georgia Georgia
Since I started this I'll give my solution found, for me
Hello All,
A certified technician has looked at my A/C (someone I know and did it for free !!!). For clarity I don't have the 'dual zone' system; I have just the manual/***** system that controls it for both driver and passenger.
We connected gauges and ran the engine at 1500 rpm's. About 1/3 of a can of refrigerant went into the system. The 'cooling' began to be noticed on the driver's side. But...it still was not equal to what was coming out on the passenger side. I told him about the info I found from you all about re-setting the actuators. We pulled the fuse and waited over 2 or 3 minutes and put it back in. Everything is running fine now.
Is there a leak in my system? We think so because we could see the 'green' dye showing on the bottom of the compressor. But it was added last fall and with only 1/3 of a can going in the leak, we're guessing, it is extremely small/slow. So....right or wrong..... I'll wait to replace the compressor and have him add refrigerant when needed.
Even though I don't have the fancy 'dual zone' I appreciated the explanation on how the cool air comes from the high side and the low side to cool the driver and the passenger....makes a lot of sense; thanks.
thanks again ya'll for the assist and the info. Much appreciated.
A certified technician has looked at my A/C (someone I know and did it for free !!!). For clarity I don't have the 'dual zone' system; I have just the manual/***** system that controls it for both driver and passenger.
We connected gauges and ran the engine at 1500 rpm's. About 1/3 of a can of refrigerant went into the system. The 'cooling' began to be noticed on the driver's side. But...it still was not equal to what was coming out on the passenger side. I told him about the info I found from you all about re-setting the actuators. We pulled the fuse and waited over 2 or 3 minutes and put it back in. Everything is running fine now.
Is there a leak in my system? We think so because we could see the 'green' dye showing on the bottom of the compressor. But it was added last fall and with only 1/3 of a can going in the leak, we're guessing, it is extremely small/slow. So....right or wrong..... I'll wait to replace the compressor and have him add refrigerant when needed.
Even though I don't have the fancy 'dual zone' I appreciated the explanation on how the cool air comes from the high side and the low side to cool the driver and the passenger....makes a lot of sense; thanks.
thanks again ya'll for the assist and the info. Much appreciated.
Melting Slicks
Joined: Jul 2006
Posts: 2,332
Likes: 31
From: Silver Spring MD
Most slow leaks are at the connectors - loose or bad O rings
Unless you have a bad rubber hose most of the slow leaks are at the places where the lines connect to something else. The O rings are freon resistant and can usually be found at a good auto parts store or a place selling AC supplies. Get a set of guages/hoses at HF for about $40 and check and charge it yourself. On a hot day (90 degrees) typical high pressure will be around 250 PSI and the low side about 30 PSI. If the high side is only 100 or 150 PSI you are probably low on freon. A full charge is slightly over 1 1/2# or about 2 12 oz cans of R134a.
\
\
Team Owner
Joined: Jul 2012
Posts: 34,479
Likes: 532
From: Central PA. - - My AR15 identifies as a muzzleloader
I believe in the Beer Fairy
Racer
Joined: Jun 2012
Posts: 459
Likes: 1
From: LAUREL MD
Hot passenger a/c
I did a search and the closest i found to my problem is "jeff in den." cool/driver -- hot/passenger. The difference being is that i am not throwing any codes. I understand that freon levels in the condenser will affect cooling -- (high section of condenser = driver cooling -- lower section of condenser = passenger cooling) but mine is opposite so i believe that can be ruled out. I also learned that due to battery leaks the vacuum/pressure lines to the actuator might be eaten through. But, again, i am not throwing codes. I am not hearing either actuator cycle as bill curlee suggests, but i may be just not hearing them. What is really confusing me is the lack of codes. If anyone has any ideas i would appreciate the input as i am not looking forward to tearing up the interior to get at the passenger actuator. Thanx.
Team Owner
Joined: Jul 2012
Posts: 34,479
Likes: 532
From: Central PA. - - My AR15 identifies as a muzzleloader
I believe in the Beer Fairy
I did a search and the closest i found to my problem is "jeff in den." cool/driver -- hot/passenger. The difference being is that i am not throwing any codes. I understand that freon levels in the condenser will affect cooling -- (high section of condenser = driver cooling -- lower section of condenser = passenger cooling) but mine is opposite so i believe that can be ruled out. I also learned that due to battery leaks the vacuum/pressure lines to the actuator might be eaten through. But, again, i am not throwing codes. I am not hearing either actuator cycle as bill curlee suggests, but i may be just not hearing them. What is really confusing me is the lack of codes. If anyone has any ideas i would appreciate the input as i am not looking forward to tearing up the interior to get at the passenger actuator. Thanx.
As to hearing them, the rest of my car makes enough noise that it's difficult for me, even now that I know what to listen for. And my hearing is quite good. On mine, my doors sorta creak like in an old scary movie, but real quiet like. I can hear mostly at the end of travel as the motor stalls while pushing on them. Then it cycles back and goes the other way. I've never heard the one on my passengers side. The sound is so slight, I bet I'd need to be down in the footwell to hear that one over the drivers side. Just be sure you're in a quiet place when you do this. If you're not throwing any codes, I'd expect they have to be cycling.
Intermediate
Joined: Dec 2008
Posts: 35
Likes: 0
From: Lawton OK
I had the same exact problem in my '99 Coupe. It was blowing nice cool air out the passenger side but hot air out the drivers side. It was the actuator that Bill C has in his post. There is a DIY somewhere on here I found for fixing the actuator. I used that and first tested the actuator motor by connecting the power leads (after I removed it) to make sure it was good. I followed the DIY procedure, disassembled the actuator, removed the large white gear (after removing the gear on top of it) and turned it 1 tooth CCW (as referenced in Bill C's pic with the shaft on top). Reassembled it and the drivers side started blowing cool air again. I'll look for the DIY and repost unless someone else finds it before me. I don't recal if they are separate post but there is also one where you remove the HVAC head and resolder some points - I did that as well.
Intermediate
Joined: Dec 2008
Posts: 35
Likes: 0
From: Lawton OK
The links are off the Ultimate DIY post. First link is what I used to fix my actuator...second link I did as preventive maintenance for the HVAC head dim/bright fix.
http://vette.tnreeds.com/actuator/actuator.htm
http://forums.corvetteforum.com/c5-t...splay-fix.html
In hind sight, I read that you did not have any codes? I believe I had one of the codes listed in the actuator fix so this may be for naught for your situation:-(
http://vette.tnreeds.com/actuator/actuator.htm
http://forums.corvetteforum.com/c5-t...splay-fix.html
In hind sight, I read that you did not have any codes? I believe I had one of the codes listed in the actuator fix so this may be for naught for your situation:-(
Last edited by TinyTimm; Jul 26, 2012 at 02:03 PM.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Pro
Joined: Feb 2002
Posts: 709
Likes: 10
From: Carlsbad CA
With a properly charged system (28oz), could it also be a high side restriction such as a partially clogged orifice tube that creates high side pressure build up at higher rpms?