Possible A/C Problem Solution
Thread Starter
Instructor
Joined: Mar 2005
Posts: 128
Likes: 0
From: Rochester New York
Possible A/C Problem Solution
Here's the latest I have from a Corvette Tech. that has diagnosed and fixed the A/C warm...cold...warm problem. (Props to Maven for his follow-up)
A/C refrigerant pressure sensor diagnosis tips:
The A/C refrigerant pressure sensor is a 3-wire piezoelectric pressure transducer. A 5-volt reference, low reference, and signal circuts 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 prevents the A/C system from operating when an excesively high or low pressure condition exists. The ECM disables the compressor clutch under the following conditions:
A/C pressure is more than 2850 kPa (413 psi).... The clutch will be enabled after the pressure decreasses to less than 2100 kPa (254 psi).
A/C pressure is less than 204 kPa (30 psi).... The clutch will be enabled after the pressure incraeses to more than 220 kPa (32 psi).
Using the Tech2 bring up the HVAC-automatiic data display list, select Engine Control Module data list.
Run the vehicle to duplicate concern, record HVAC system snapshot with Tech2.
After recording snapshot of events, review data, looking for a/c pressures outside of normal operating range, also be SURE to look at the A/C disengage history ...it will show the last 8 events that caused the A/C to shut off.
Be sure to ask the technician/SM "isnt there some way to find out what keeps shutting off the A/C.....doesn't the computer keep track???"
They SHOULD know about the a/c engagement history data parameter....if they dont....think of someway to tell them...whether it be straight out ask them to look further into the data for an answer....
There is invaluable data in those eight little lines of info on the Tech2!!
A/C refrigerant pressure sensor diagnosis tips:
The A/C refrigerant pressure sensor is a 3-wire piezoelectric pressure transducer. A 5-volt reference, low reference, and signal circuts 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 prevents the A/C system from operating when an excesively high or low pressure condition exists. The ECM disables the compressor clutch under the following conditions:
A/C pressure is more than 2850 kPa (413 psi).... The clutch will be enabled after the pressure decreasses to less than 2100 kPa (254 psi).
A/C pressure is less than 204 kPa (30 psi).... The clutch will be enabled after the pressure incraeses to more than 220 kPa (32 psi).
Using the Tech2 bring up the HVAC-automatiic data display list, select Engine Control Module data list.
Run the vehicle to duplicate concern, record HVAC system snapshot with Tech2.
After recording snapshot of events, review data, looking for a/c pressures outside of normal operating range, also be SURE to look at the A/C disengage history ...it will show the last 8 events that caused the A/C to shut off.
Be sure to ask the technician/SM "isnt there some way to find out what keeps shutting off the A/C.....doesn't the computer keep track???"
They SHOULD know about the a/c engagement history data parameter....if they dont....think of someway to tell them...whether it be straight out ask them to look further into the data for an answer....
There is invaluable data in those eight little lines of info on the Tech2!!
Last edited by RevDice; Jun 19, 2005 at 12:56 AM.
Thread Starter
Instructor
Joined: Mar 2005
Posts: 128
Likes: 0
From: Rochester New York
Part Numbers as posted from Maven...
The A/C Refrigerant pressure sensor is one of two part #'s. #22678731 for aluminum or #22634172 for steel
the cars uses one or the other, not both and there are just two different designs, one is better than the other.
He didn't say which was better...I'm guessing aluminum.
I'm going to pursue this fix. If anyone beats me to it let me know how you make out.
The A/C Refrigerant pressure sensor is one of two part #'s. #22678731 for aluminum or #22634172 for steel
the cars uses one or the other, not both and there are just two different designs, one is better than the other.
He didn't say which was better...I'm guessing aluminum.
I'm going to pursue this fix. If anyone beats me to it let me know how you make out.
Thread Starter
Instructor
Joined: Mar 2005
Posts: 128
Likes: 0
From: Rochester New York
Originally Posted by austinC6
RevDice, this is excellent information. Not only a suspect part, but a way to get the problem history, and a simple fix. I appreciate your diagnostic skills and detective work. 
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Thread Starter
Instructor
Joined: Mar 2005
Posts: 128
Likes: 0
From: Rochester New York
Originally Posted by jfloresfsu
RevDice,
Are your problems solved? Has the problem reoccurred since the sensors were changed?
Are your problems solved? Has the problem reoccurred since the sensors were changed?
Instructor
Joined: Mar 2005
Posts: 151
Likes: 1
From: Green Bay WI
Originally Posted by RevDice
Here's the latest I have from a Corvette Tech. that has diagnosed and fixed the A/C warm...cold...warm problem. (Props to Maven for his follow-up)
A/C refrigerant pressure sensor diagnosis tips:
The A/C refrigerant pressure sensor is a 3-wire piezoelectric pressure transducer. A 5-volt reference, low reference, and signal circuts 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 prevents the A/C system from operating when an excesively high or low pressure condition exists. The ECM disables the compressor clutch under the following conditions:
A/C pressure is more than 2850 kPa (413 psi).... The clutch will be enabled after the pressure decreasses to less than 2100 kPa (254 psi).
A/C pressure is less than 204 kPa (30 psi).... The clutch will be enabled after the pressure incraeses to more than 220 kPa (32 psi).
Using the Tech2 bring up the HVAC-automatiic data display list, select Engine Control Module data list.
Run the vehicle to duplicate concern, record HVAC system snapshot with Tech2.
After recording snapshot of events, review data, looking for a/c pressures outside of normal operating range, also be SURE to look at the A/C disengage history ...it will show the last 8 events that caused the A/C to shut off.
Be sure to ask the technician/SM "isnt there some way to find out what keeps shutting off the A/C.....doesn't the computer keep track???"
They SHOULD know about the a/c engagement history data parameter....if they dont....think of someway to tell them...whether it be straight out ask them to look further into the data for an answer....
There is invaluable data in those eight little lines of info on the Tech2!!
A/C refrigerant pressure sensor diagnosis tips:
The A/C refrigerant pressure sensor is a 3-wire piezoelectric pressure transducer. A 5-volt reference, low reference, and signal circuts 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 prevents the A/C system from operating when an excesively high or low pressure condition exists. The ECM disables the compressor clutch under the following conditions:
A/C pressure is more than 2850 kPa (413 psi).... The clutch will be enabled after the pressure decreasses to less than 2100 kPa (254 psi).
A/C pressure is less than 204 kPa (30 psi).... The clutch will be enabled after the pressure incraeses to more than 220 kPa (32 psi).
Using the Tech2 bring up the HVAC-automatiic data display list, select Engine Control Module data list.
Run the vehicle to duplicate concern, record HVAC system snapshot with Tech2.
After recording snapshot of events, review data, looking for a/c pressures outside of normal operating range, also be SURE to look at the A/C disengage history ...it will show the last 8 events that caused the A/C to shut off.
Be sure to ask the technician/SM "isnt there some way to find out what keeps shutting off the A/C.....doesn't the computer keep track???"
They SHOULD know about the a/c engagement history data parameter....if they dont....think of someway to tell them...whether it be straight out ask them to look further into the data for an answer....
There is invaluable data in those eight little lines of info on the Tech2!!
Thanks for the info! So is the "fix" replacing the pressure sensor? I'm calling my dealer tomorrow to set up an appointment, and am printing out your info to hand to them!
Racer
Joined: Dec 2004
Posts: 443
Likes: 1
From: AZ
Well, it sure sounds convincing to me.
AZ heat is up to 110+. I've been on vacation in San Diego for the last week so I haven't driven my C6 in the new heat to see if it acts up again.
I hope my has fixed itself. Yeah, like that's going to happen.
Thanks for the info!
AZ heat is up to 110+. I've been on vacation in San Diego for the last week so I haven't driven my C6 in the new heat to see if it acts up again.
I hope my has fixed itself. Yeah, like that's going to happen.
Thanks for the info!
Drifting
Joined: Sep 2004
Posts: 1,835
Likes: 295
From: Phoenix AZ
Originally Posted by RevDice
Here's the latest I have from a Corvette Tech. that has diagnosed and fixed the A/C warm...cold...warm problem. (Props to Maven for his follow-up)
A/C refrigerant pressure sensor diagnosis tips:
The A/C refrigerant pressure sensor is a 3-wire piezoelectric pressure transducer. A 5-volt reference, low reference, and signal circuts 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 prevents the A/C system from operating when an excesively high or low pressure condition exists. The ECM disables the compressor clutch under the following conditions:
A/C pressure is more than 2850 kPa (413 psi).... The clutch will be enabled after the pressure decreasses to less than 2100 kPa (254 psi).
A/C pressure is less than 204 kPa (30 psi).... The clutch will be enabled after the pressure incraeses to more than 220 kPa (32 psi).
Using the Tech2 bring up the HVAC-automatiic data display list, select Engine Control Module data list.
Run the vehicle to duplicate concern, record HVAC system snapshot with Tech2.
After recording snapshot of events, review data, looking for a/c pressures outside of normal operating range, also be SURE to look at the A/C disengage history ...it will show the last 8 events that caused the A/C to shut off.
Be sure to ask the technician/SM "isnt there some way to find out what keeps shutting off the A/C.....doesn't the computer keep track???"
They SHOULD know about the a/c engagement history data parameter....if they dont....think of someway to tell them...whether it be straight out ask them to look further into the data for an answer....
There is invaluable data in those eight little lines of info on the Tech2!!
A/C refrigerant pressure sensor diagnosis tips:
The A/C refrigerant pressure sensor is a 3-wire piezoelectric pressure transducer. A 5-volt reference, low reference, and signal circuts 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 prevents the A/C system from operating when an excesively high or low pressure condition exists. The ECM disables the compressor clutch under the following conditions:
A/C pressure is more than 2850 kPa (413 psi).... The clutch will be enabled after the pressure decreasses to less than 2100 kPa (254 psi).
A/C pressure is less than 204 kPa (30 psi).... The clutch will be enabled after the pressure incraeses to more than 220 kPa (32 psi).
Using the Tech2 bring up the HVAC-automatiic data display list, select Engine Control Module data list.
Run the vehicle to duplicate concern, record HVAC system snapshot with Tech2.
After recording snapshot of events, review data, looking for a/c pressures outside of normal operating range, also be SURE to look at the A/C disengage history ...it will show the last 8 events that caused the A/C to shut off.
Be sure to ask the technician/SM "isnt there some way to find out what keeps shutting off the A/C.....doesn't the computer keep track???"
They SHOULD know about the a/c engagement history data parameter....if they dont....think of someway to tell them...whether it be straight out ask them to look further into the data for an answer....
There is invaluable data in those eight little lines of info on the Tech2!!
However, unless I am missing something, there is no information how to correct the above.
Has anyone fixed their A/C issue yet?
Rob
Instructor
Joined: Jan 2005
Posts: 144
Likes: 2
From: Austin Texas
I just talked to my service guy, who has been diligently pursuing the resolution of this problem for me. He has already replaced the thermal expansion valve, with no success. He was planning on replacing the compressor as his next plan of attack, until I showed him the info in this thread. He did some more testing, and since he had a pressure sensor in stock, he replaced it just to be sure. The problem persists.
He made some good observations regarding the pressure sensor. Apparently there are many customers who have complained to GM about this A/C problem. Many have had the problem resolved by changing the sensor. The sensor was causing the compressor to kick off when it shouldn't, which can be verified via the computer readout. However, my problem seems to be different, as the compressor isn't kicking off. This is an important point to observe on any car experiencing the problem.
In my case, the pressure is simply fluctuating, causing the effectiveness of the cooling to suffer. Why this is happening is still unknown, but we suspect a design issue with the thermal expansion valve. The valve will be observed while the problem occurs (not difficult on my car), for any mechanical noises or vibrations that may indicate it working correctly or not. We will probably still have to change the compressor, just to rule that out. If that doesn't work...
So, are your compressors disengaging or do you have my problem?
He made some good observations regarding the pressure sensor. Apparently there are many customers who have complained to GM about this A/C problem. Many have had the problem resolved by changing the sensor. The sensor was causing the compressor to kick off when it shouldn't, which can be verified via the computer readout. However, my problem seems to be different, as the compressor isn't kicking off. This is an important point to observe on any car experiencing the problem.
In my case, the pressure is simply fluctuating, causing the effectiveness of the cooling to suffer. Why this is happening is still unknown, but we suspect a design issue with the thermal expansion valve. The valve will be observed while the problem occurs (not difficult on my car), for any mechanical noises or vibrations that may indicate it working correctly or not. We will probably still have to change the compressor, just to rule that out. If that doesn't work...
So, are your compressors disengaging or do you have my problem?
Racer
Joined: Dec 2004
Posts: 443
Likes: 1
From: AZ
Originally Posted by austinC6
I just talked to my service guy, who has been diligently pursuing the resolution of this problem for me. He has already replaced the thermal expansion valve, with no success. He was planning on replacing the compressor as his next plan of attack, until I showed him the info in this thread. He did some more testing, and since he had a pressure sensor in stock, he replaced it just to be sure. The problem persists.
He made some good observations regarding the pressure sensor. Apparently there are many customers who have complained to GM about this A/C problem. Many have had the problem resolved by changing the sensor. The sensor was causing the compressor to kick off when it shouldn't, which can be verified via the computer readout. However, my problem seems to be different, as the compressor isn't kicking off. This is an important point to observe on any car experiencing the problem.
In my case, the pressure is simply fluctuating, causing the effectiveness of the cooling to suffer. Why this is happening is still unknown, but we suspect a design issue with the thermal expansion valve. The valve will be observed while the problem occurs (not difficult on my car), for any mechanical noises or vibrations that may indicate it working correctly or not. We will probably still have to change the compressor, just to rule that out. If that doesn't work...
So, are your compressors disengaging or do you have my problem?
He made some good observations regarding the pressure sensor. Apparently there are many customers who have complained to GM about this A/C problem. Many have had the problem resolved by changing the sensor. The sensor was causing the compressor to kick off when it shouldn't, which can be verified via the computer readout. However, my problem seems to be different, as the compressor isn't kicking off. This is an important point to observe on any car experiencing the problem.
In my case, the pressure is simply fluctuating, causing the effectiveness of the cooling to suffer. Why this is happening is still unknown, but we suspect a design issue with the thermal expansion valve. The valve will be observed while the problem occurs (not difficult on my car), for any mechanical noises or vibrations that may indicate it working correctly or not. We will probably still have to change the compressor, just to rule that out. If that doesn't work...
So, are your compressors disengaging or do you have my problem?
If I remember correctly, it seems as if the volume of air fluctuates greatly as this problem occurs. It goes from high to low when it gets hot and then seems to blow high and hot/moist again. I didn't have the brains to switch on/off the manual compressor snowflake when it was happening either. The cooling fan in the engine continued to run on the car, however, after it was shut off for what appeared to be an excessive amount of time.
This could be considered Lemon Law qualifying, if GM can't fix it, at least in 115 degree Arizona!
You could friggin die in this heat without A/C.
Instructor
Joined: Jan 2005
Posts: 144
Likes: 2
From: Austin Texas
Originally Posted by DebtCraft
That is good info! My problem hasn't surfaced again (YET, OF COURSE) so I don't know if the compressor isn't kicking on or off.
If I remember correctly, it seems as if the volume of air fluctuates greatly as this problem occurs. It goes from high to low when it gets hot and then seems to blow high and hot/moist again. I didn't have the brains to switch on/off the manual compressor snowflake when it was happening either. The cooling fan in the engine continued to run on the car, however, after it was shut off for what appeared to be an excessive amount of time.
This could be considered Lemon Law qualifying, if GM can't fix it, at least in 115 degree Arizona! You could friggin die in this heat without A/C.
If I remember correctly, it seems as if the volume of air fluctuates greatly as this problem occurs. It goes from high to low when it gets hot and then seems to blow high and hot/moist again. I didn't have the brains to switch on/off the manual compressor snowflake when it was happening either. The cooling fan in the engine continued to run on the car, however, after it was shut off for what appeared to be an excessive amount of time.
This could be considered Lemon Law qualifying, if GM can't fix it, at least in 115 degree Arizona!
You could friggin die in this heat without A/C.
Instructor
Joined: Nov 2003
Posts: 243
Likes: 8
From: San Antonio TX
I chased a similar issue on my C5 for 4 years. It would consistently freeze you out when set at 60 degrees. Set it on 61 and you might get 61 or 120 degrees. At times, one side of the vents would blow cold and the other hot. Bottom line was that they replaced every part they could think of. It seemed to work for a short while and start again. They never found the problem. I put extended warranty on it for that reason. It was about to expire so I bought a C6. I now seem to have the problem where it shuts of from time to time for no apparent reason. Seems to me that GM hasn't a clue on how to A/C a Corvette properly. 
Thread Starter
Instructor
Joined: Mar 2005
Posts: 128
Likes: 0
From: Rochester New York
Originally Posted by austinC6
I just talked to my service guy, who has been diligently pursuing the resolution of this problem for me. He has already replaced the thermal expansion valve, with no success. He was planning on replacing the compressor as his next plan of attack, until I showed him the info in this thread. He did some more testing, and since he had a pressure sensor in stock, he replaced it just to be sure. The problem persists.
He made some good observations regarding the pressure sensor. Apparently there are many customers who have complained to GM about this A/C problem. Many have had the problem resolved by changing the sensor. The sensor was causing the compressor to kick off when it shouldn't, which can be verified via the computer readout. However, my problem seems to be different, as the compressor isn't kicking off. This is an important point to observe on any car experiencing the problem.
In my case, the pressure is simply fluctuating, causing the effectiveness of the cooling to suffer. Why this is happening is still unknown, but we suspect a design issue with the thermal expansion valve. The valve will be observed while the problem occurs (not difficult on my car), for any mechanical noises or vibrations that may indicate it working correctly or not. We will probably still have to change the compressor, just to rule that out. If that doesn't work...
So, are your compressors disengaging or do you have my problem?
He made some good observations regarding the pressure sensor. Apparently there are many customers who have complained to GM about this A/C problem. Many have had the problem resolved by changing the sensor. The sensor was causing the compressor to kick off when it shouldn't, which can be verified via the computer readout. However, my problem seems to be different, as the compressor isn't kicking off. This is an important point to observe on any car experiencing the problem.
In my case, the pressure is simply fluctuating, causing the effectiveness of the cooling to suffer. Why this is happening is still unknown, but we suspect a design issue with the thermal expansion valve. The valve will be observed while the problem occurs (not difficult on my car), for any mechanical noises or vibrations that may indicate it working correctly or not. We will probably still have to change the compressor, just to rule that out. If that doesn't work...
So, are your compressors disengaging or do you have my problem?
Thanks for posting austin. This is discouraging stuff. I'm scheduled to bring my Vette in on Monday the 27th. The dealer has already ordered the part for replacement. My compressor seems to be disengaging. I can get it back on most times by hitting the snowflake button (off/on). I'll post after the sensor is replaced.
I feel for you guys in that 115 degree heat. In the low 80's here and I miss my air. You guys have to be...
Instructor
Joined: Jan 2005
Posts: 144
Likes: 2
From: Austin Texas
Originally Posted by RevDice
Thanks for posting austin. This is discouraging stuff. I'm scheduled to bring my Vette in on Monday the 27th. The dealer has already ordered the part for replacement. My compressor seems to be disengaging. I can get it back on most times by hitting the snowflake button (off/on). I'll post after the sensor is replaced.
I feel for you guys in that 115 degree heat. In the low 80's here and I miss my air. You guys have to be...
I feel for you guys in that 115 degree heat. In the low 80's here and I miss my air. You guys have to be...