HVAC Perfect but Wrong!!
Le Mans Master
Joined: May 2006
Posts: 5,987
Likes: 18
From: DuBois PA
St. Jude Donor '11-'12-'13-'14-'15
I went over EVERYTHING one more time and the problem is fixed. You won't believe what I found! (Well, maybe you will).
The first thing that I found was that sitting in one place idling for a long time causes the entire tunnel area to heat up tremedously. This pushes the driver's side temp up. When I took the car for a drive, I actually got the air at the driver's side vents to drop from 88 degrees to 62 degrees (Still not good enough).
Then I went over the specs in the factory manual and noted that the recommended system pressures seemed a bit low compared to other charts that I had for ambient air and humidity.
The factory manual was calling for 27 psi/ low side and 135 psi/ high side at 1,000 RPM. I finally decided that I had nothing else to lose (but a compressor) and added more R-134a to raise the pressures to about 30 psi/low side and 250 psi/high side. Ambient is about 82 degrees this morning.
I now have 42 degrees at the center vent on the driver's side and 40 degrees at the left vent on the passenger's side of the dash. The factory manual calls for 40 degrees on a perfect system.
Everything is running fine with no unusual noises. I should have gone with my gut feeling about those pressures from the beginning. Anyway......the thing about low freon causing high temps on the driver's side is right on the money though it makes no sense to me since there is one common evaporator. The temp control doors were completely shot and that just added to the problem. On the good side, I now know this HVAC system inside and out. That is important here in the desert.
Thanks to everyone for their help.
--Al
The first thing that I found was that sitting in one place idling for a long time causes the entire tunnel area to heat up tremedously. This pushes the driver's side temp up. When I took the car for a drive, I actually got the air at the driver's side vents to drop from 88 degrees to 62 degrees (Still not good enough).
Then I went over the specs in the factory manual and noted that the recommended system pressures seemed a bit low compared to other charts that I had for ambient air and humidity.
The factory manual was calling for 27 psi/ low side and 135 psi/ high side at 1,000 RPM. I finally decided that I had nothing else to lose (but a compressor) and added more R-134a to raise the pressures to about 30 psi/low side and 250 psi/high side. Ambient is about 82 degrees this morning.
I now have 42 degrees at the center vent on the driver's side and 40 degrees at the left vent on the passenger's side of the dash. The factory manual calls for 40 degrees on a perfect system.
Everything is running fine with no unusual noises. I should have gone with my gut feeling about those pressures from the beginning. Anyway......the thing about low freon causing high temps on the driver's side is right on the money though it makes no sense to me since there is one common evaporator. The temp control doors were completely shot and that just added to the problem. On the good side, I now know this HVAC system inside and out. That is important here in the desert.
Thanks to everyone for their help.
--Al
FYI I lined my tunnel with the duct insulation from Frost king and totally killed all heat coming up through that area. It might be worth a shot there in the desert!
Melting Slicks
Joined: Mar 2001
Posts: 2,482
Likes: 0
From: Worden Illinois
Melting Slicks
Joined: Mar 2004
Posts: 2,149
Likes: 6
From: NCCO Oklahoma
You sir, are the man! 
I have been having the same problem for about a year. (I didn't play with it over the winter... but now that it is getting warmer...)
I have hot air out of the drivers side but cold air out of the passenger side... HAS to be the dampers, right?
I tore the dash apart, checked the actuators, pulled an actuator and took it apart, did the actuator re-learn procedure, tried another AC climate control head unit...
Today I went so far as to bid on a 'replacement' damper system/heater core/evaporator to test on the bench... just to see WTF the damper doors were doing to keep the heat flowing out the drivers side.
I have had a can of freon on the shelf for over a year, but figured it had to be something more difficult than that, right?
To think I am certified to work on everything from box units to 250 ton chiller units...
Thanks for the post! You saved what is left of my hair on my head. I now blow 40 degree air from all of my ducts!
Mark
I have been having the same problem for about a year. (I didn't play with it over the winter... but now that it is getting warmer...)
I have hot air out of the drivers side but cold air out of the passenger side... HAS to be the dampers, right?
I tore the dash apart, checked the actuators, pulled an actuator and took it apart, did the actuator re-learn procedure, tried another AC climate control head unit...
Today I went so far as to bid on a 'replacement' damper system/heater core/evaporator to test on the bench... just to see WTF the damper doors were doing to keep the heat flowing out the drivers side.
I have had a can of freon on the shelf for over a year, but figured it had to be something more difficult than that, right?
To think I am certified to work on everything from box units to 250 ton chiller units...
Thanks for the post! You saved what is left of my hair on my head. I now blow 40 degree air from all of my ducts!
Mark
Last edited by Fasthotrod; May 28, 2007 at 12:35 AM.
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Melting Slicks
Joined: May 2006
Posts: 2,936
Likes: 260
From: Westchester County New York
I had the same issue...hot air on drivers side...not so cold air on passenger side....had Chuck at Corvettes of Westchester charge me up...NOW I can hang meat in the car its so cold...
Melting Slicks
Joined: Mar 2004
Posts: 2,149
Likes: 6
From: NCCO Oklahoma
When a system is low on charge, there just isn't enough 'heat carriers' to remove the heat from the system. The refrigerant becomes saturated with heat too soon in the process... and is very inefficient.
Think of the evaporator core for a second. It has an entry point, and an exit point. The entry point is where the refrigerant changes from liquid to vapor form, which causes the cooling effect. (Pressure and temperature are directly related. A drop in pressure = drop in temperature.)
In the C5, the 'start' point for the evaporator must be on the passenger side of the ventilation system... whereas the 'end' of the evaporator core must be on the drivers side of the ventilation system. When the system is low on refrigerant, the only cooling effect that happens is in the beginning part of the evaporator core... it just becomes heat saturated by the time it reaches the end. Thus: No cooling on the drivers side.
It's the only thing that makes sense to me... I'll know more when I get my replacement damper system in and can verify it.
One thing that should have stood out to me was this: The cooling on the passenger side, while cool, was not within specifications. I should have caught that first... but I ***umed that the climate controller was keeping the temperature output at 60 degrees. The manual clearly says 40 degrees at max cooling.
Mark
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,396
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
TTT 
This is a significantly important post! It needs to be constantly recirculated!
There are LOTS of people out there right now that have less than perfect AC Systems.
BC
This is a significantly important post! It needs to be constantly recirculated!
There are LOTS of people out there right now that have less than perfect AC Systems.
BC
1st Gear
Joined: Jun 2010
Posts: 1
Likes: 0
AC Blowing Heat on Passenger, Cold on Driver Actuator stuck?
Hi All, wanna thank you for ideas ,,,,I had a problem with Heater blowing thru passenger while cold air thru driver. Was told that i needed to resynchronize actuators...I was told that sometimes when battery dies or changinf batteries actuators need to be reset. While the car was running i took out fuse # 27 in passenger foot fuse panel out and pout it back on..Made it worse cause now i was getting heater thru both sides...Fustrated i waited a few minutes, pulled the fuse out while the car was running and turned the car off.. I put the fuse back in and then turned on the car and bang, after 20-30 seconds, i was getting cold air on both sides...
Apaprently these acutators need to be reset so that solved my problem...hope this helps someone because i was about to buy a control panel and would have wasted my money..
Apaprently these acutators need to be reset so that solved my problem...hope this helps someone because i was about to buy a control panel and would have wasted my money..
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,396
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
If the HVAC Acutator DTCs are set, it wont sync. I turn the HVAC OFF clear the fuse and then turn it on. Usually clears the issue right up. A couple of times it took more than one try. Disconnecting the battery most likely reset that dTC
Bill
Bill
Melting Slicks
Joined: Sep 2006
Posts: 2,736
Likes: 7
From: Redding CA
I think I know... I'll explain it as best as I can, without boring you with too much techno-babble.
When a system is low on charge, there just isn't enough 'heat carriers' to remove the heat from the system. The refrigerant becomes saturated with heat too soon in the process... and is very inefficient.
Think of the evaporator core for a second. It has an entry point, and an exit point. The entry point is where the refrigerant changes from liquid to vapor form, which causes the cooling effect. (Pressure and temperature are directly related. A drop in pressure = drop in temperature.)
In the C5, the 'start' point for the evaporator must be on the passenger side of the ventilation system... whereas the 'end' of the evaporator core must be on the drivers side of the ventilation system. When the system is low on refrigerant, the only cooling effect that happens is in the beginning part of the evaporator core... it just becomes heat saturated by the time it reaches the end. Thus: No cooling on the drivers side.
It's the only thing that makes sense to me... I'll know more when I get my replacement damper system in and can verify it.
One thing that should have stood out to me was this: The cooling on the passenger side, while cool, was not within specifications. I should have caught that first... but I ***umed that the climate controller was keeping the temperature output at 60 degrees. The manual clearly says 40 degrees at max cooling.
Mark
When a system is low on charge, there just isn't enough 'heat carriers' to remove the heat from the system. The refrigerant becomes saturated with heat too soon in the process... and is very inefficient.
Think of the evaporator core for a second. It has an entry point, and an exit point. The entry point is where the refrigerant changes from liquid to vapor form, which causes the cooling effect. (Pressure and temperature are directly related. A drop in pressure = drop in temperature.)
In the C5, the 'start' point for the evaporator must be on the passenger side of the ventilation system... whereas the 'end' of the evaporator core must be on the drivers side of the ventilation system. When the system is low on refrigerant, the only cooling effect that happens is in the beginning part of the evaporator core... it just becomes heat saturated by the time it reaches the end. Thus: No cooling on the drivers side.
It's the only thing that makes sense to me... I'll know more when I get my replacement damper system in and can verify it.
One thing that should have stood out to me was this: The cooling on the passenger side, while cool, was not within specifications. I should have caught that first... but I ***umed that the climate controller was keeping the temperature output at 60 degrees. The manual clearly says 40 degrees at max cooling.
Mark
Very well said here man. I read through a post the Bill sent me "AC 101"...this is the reason for low R 134 giving a low temp on one side and it is going to be my issue I am about 99 percent sure
Burning Brakes
Joined: Jan 2010
Posts: 763
Likes: 0
From: Murfreesboro TN
I added 24 ounces of R134A freon and that fixed it!
To anyone else troubleshooting this issue...
My charge was low enough that the suction line to the compressor didn't even sweat, but was blowing very cold air out of the passenger side and 70-80*F air from the driver's side.
Also the high pressure hose side was only a few degrees warmer than the suction side until after the first can was added.
According to the chart that came with the refill kit and hose/gauge. The 100*F ambient temps required 50-55 psi suction pressure. I refilled using the guide and the A/C now performes perfectly! =)
If anyone wants the R134A pressure/temperature chart, let me know and I will take a picture of it and attach it to this thread.
The first 12 ounce can made the suction line sweat immediately, the second can made the driver side as cold as the passenger side vents. =).
I got to enjoy the 97-98*F day with the A/C set to 68*F and it ran perfectly in auto A/C. It even gave me the shivers.
To anyone else troubleshooting this issue...
My charge was low enough that the suction line to the compressor didn't even sweat, but was blowing very cold air out of the passenger side and 70-80*F air from the driver's side.
Also the high pressure hose side was only a few degrees warmer than the suction side until after the first can was added.
According to the chart that came with the refill kit and hose/gauge. The 100*F ambient temps required 50-55 psi suction pressure. I refilled using the guide and the A/C now performes perfectly! =)
If anyone wants the R134A pressure/temperature chart, let me know and I will take a picture of it and attach it to this thread.
The first 12 ounce can made the suction line sweat immediately, the second can made the driver side as cold as the passenger side vents. =).
I got to enjoy the 97-98*F day with the A/C set to 68*F and it ran perfectly in auto A/C. It even gave me the shivers.
Racer
Joined: Jul 2004
Posts: 282
Likes: 2
From: Wappingers Falls NY
Ac chart
I added 24 ounces of R134A freon and that fixed it!
To anyone else troubleshooting this issue...
My charge was low enough that the suction line to the compressor didn't even sweat, but was blowing very cold air out of the passenger side and 70-80*F air from the driver's side.
Also the high pressure hose side was only a few degrees warmer than the suction side until after the first can was added.
According to the chart that came with the refill kit and hose/gauge. The 100*F ambient temps required 50-55 psi suction pressure. I refilled using the guide and the A/C now performes perfectly! =)
If anyone wants the R134A pressure/temperature chart, let me know and I will take a picture of it and attach it to this thread.
The first 12 ounce can made the suction line sweat immediately, the second can made the driver side as cold as the passenger side vents. =).
I got to enjoy the 97-98*F day with the A/C set to 68*F and it ran perfectly in auto A/C. It even gave me the shivers.
To anyone else troubleshooting this issue...
My charge was low enough that the suction line to the compressor didn't even sweat, but was blowing very cold air out of the passenger side and 70-80*F air from the driver's side.
Also the high pressure hose side was only a few degrees warmer than the suction side until after the first can was added.
According to the chart that came with the refill kit and hose/gauge. The 100*F ambient temps required 50-55 psi suction pressure. I refilled using the guide and the A/C now performes perfectly! =)
If anyone wants the R134A pressure/temperature chart, let me know and I will take a picture of it and attach it to this thread.
The first 12 ounce can made the suction line sweat immediately, the second can made the driver side as cold as the passenger side vents. =).
I got to enjoy the 97-98*F day with the A/C set to 68*F and it ran perfectly in auto A/C. It even gave me the shivers.
Medic23w@verizon.net