Unusual A/C issue.....PLEASE HELP!!!
Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
Unusual A/C issue.....PLEASE HELP!!! Good morning forum members. I'm really hoping someone can help me out on this. I did get a reply on this once, from a member who sounded like he knew what he was talking about. BUT-I LOST THE REPLY!!!! Here goes.........
I have a very unusual A/C problem. First off, I have a 2000 C5, an A4. A/C AND cooling FANS, HI SPEED AND LOW, BOTH WORK as they're supposed to........EXCEPT at a standstill, when car has come to a conplete stop. Fans still work, but A/C compressor disengages when you are completely stopped!! As long as you're moving, even at 1mph, all is well. But when you stop completely, it disengages the compressor!!! DOH!!!!!! In Michigan, this isn't that big of a deal, as the red lights aren't that long. But when I'm in Florida, some of these damn red lights are long enough to get out your Norelco, shave, and clean the thing. I'm not exaggerating!! Floridians know what I'm saying. Anyway, someone here mentioned there's a setting in the car's PCM that can cause this, but I can't find the post!!! Since my car never did this until I put a cam in it, then had it tuned, I'm thinking the tuner did this so the car might idle better at the red lights, if it wasn't spinning the compressor. I have someone with HP Tuners, who is willing to try to tune this out, but doesn't know where to look in his tuning suite for it. He called it a "tab" (?). I'm sure hoping you guys will help me out on this. It's very annoying. Thank you in advance..........
I have a very unusual A/C problem. First off, I have a 2000 C5, an A4. A/C AND cooling FANS, HI SPEED AND LOW, BOTH WORK as they're supposed to........EXCEPT at a standstill, when car has come to a conplete stop. Fans still work, but A/C compressor disengages when you are completely stopped!! As long as you're moving, even at 1mph, all is well. But when you stop completely, it disengages the compressor!!! DOH!!!!!! In Michigan, this isn't that big of a deal, as the red lights aren't that long. But when I'm in Florida, some of these damn red lights are long enough to get out your Norelco, shave, and clean the thing. I'm not exaggerating!! Floridians know what I'm saying. Anyway, someone here mentioned there's a setting in the car's PCM that can cause this, but I can't find the post!!! Since my car never did this until I put a cam in it, then had it tuned, I'm thinking the tuner did this so the car might idle better at the red lights, if it wasn't spinning the compressor. I have someone with HP Tuners, who is willing to try to tune this out, but doesn't know where to look in his tuning suite for it. He called it a "tab" (?). I'm sure hoping you guys will help me out on this. It's very annoying. Thank you in advance..........
Last edited by grinder11; Jan 11, 2022 at 08:58 AM.
Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
Really appreciate you guys trying to help. Not a low charge, because I can put it in neutral and coast at idle speed, and it'll freeze your **** right outta there, lol. This last thing concerns one other detail. That is this:
The compressor does not disengage when stopped on rare occasions, maybe only once every 30 or 40 stops. When that happens, and while it is still engaged at the red light, as soon as I shift from OD/D and put the selector in Neutral, it disengages immediately!!!! If I'm driving, say 10-15mph, and shift to Neutral, it won't disengage!!! This is starting to drive me nuts
, and some will say it won't be a long drive!!!
The compressor does not disengage when stopped on rare occasions, maybe only once every 30 or 40 stops. When that happens, and while it is still engaged at the red light, as soon as I shift from OD/D and put the selector in Neutral, it disengages immediately!!!! If I'm driving, say 10-15mph, and shift to Neutral, it won't disengage!!! This is starting to drive me nuts
, and some will say it won't be a long drive!!! Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
Trending Topics
Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
As I said previously, someone a year or two ago posted what appeared to be the answer, but I lost the posts. Enough time has lapsed that I don't even remember if he answered me here on LS1 Tech, or a well known C5 forum. DAMN!!!!!
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
Last edited by grinder11; Jan 12, 2022 at 03:05 PM.
Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
On The Tree
Joined: Jul 2009
Posts: 151
Likes: 5
From: GA
I know my Pro EFI has settings to control the clutch on the AC in certain scenarios, VSS being one of them. I would think your PCM might as well. Might not be under the AC Section, sounds like the tune is doing this since its so specific.
Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
) said a setting does exist for this, but the question is.....Where??? I'm trying to look up my previous posts to find it, but that may be VERY time consuming, as I don't know for sure which forum I got that reply. Thank you VERY much for trying to help. I'm open to suggestions. Another problem is the car has been doing this since its original dyno tune in 2005. The subsequent tune people probably wouldn't have looked at whichever tables would do this. Even if I could find the original tune guy, would he remember what he did, or how he did this, 16-17 years ago? I have tried to locate the original tune guy, but the place he worked at is out of business. So I need an expert tuner. Car was done with HP Tuners. Wonder if they would know where in the software to look?? Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
EDIT!!!! NOW I see what you're trying to say. You're saying the ECM/PCM may be giving the BCM the signal. So it wouldn't matter how many BCMs were tried. Yes, I believe the ECM/PCM is doing this, but I also believed it was a deliberate effort by the tuner, to obtain a better-in-drive idle at stop lights. Question is, since this originated with an HP Tuners program, how and where in the HP Tuners software do you locate it, and remove it?
Last edited by grinder11; Jan 13, 2022 at 10:15 AM.
Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
The worst part is, not only do you lose cooling at stop lights, but when compressor disengages, idle speed goes up, then when it's settled back to normal, compressor engages again, and idle dives to 400-500rpm. Then just as the PCM tries to raise the idle, it disengeges again, and idle goes up to 1,200rpm. Then the whole process repeats, which makes the idle hunt constantly. This defeats the very reason it was done!!! Car idles fine with A/C on, on the rare occasions it stays engaged at a stop. Of course, idle is fine with A/C selected off, too.
On The Tree
Joined: Jul 2009
Posts: 151
Likes: 5
From: GA
I believe you're correct, as someone here, or on a well known Vette forum (can't remember which!!!) said a setting does exist for this, but the question is.....Where??? I'm trying to look up my previous posts to find it, but that may be VERY time consuming, as I don't know for sure which forum I got that reply. Thank you VERY much for trying to help. I'm open to suggestions. Another problem is the car has been doing this since its original dyno tune in 2005. The subsequent tune people probably wouldn't have looked at whichever tables would do this. Even if I could find the original tune guy, would he remember what he did, or how he did this, 16-17 years ago? I have tried to locate the original tune guy, but the place he worked at is out of business. So I need an expert tuner. Car was done with HP Tuners. Wonder if they would know where in the software to look??
) said a setting does exist for this, but the question is.....Where??? I'm trying to look up my previous posts to find it, but that may be VERY time consuming, as I don't know for sure which forum I got that reply. Thank you VERY much for trying to help. I'm open to suggestions. Another problem is the car has been doing this since its original dyno tune in 2005. The subsequent tune people probably wouldn't have looked at whichever tables would do this. Even if I could find the original tune guy, would he remember what he did, or how he did this, 16-17 years ago? I have tried to locate the original tune guy, but the place he worked at is out of business. So I need an expert tuner. Car was done with HP Tuners. Wonder if they would know where in the software to look??He sent me this following my post, he said get a screen shot of the Stall Protect and AC Torque settings and post it to HP tuners forums for help if nothing make sense
Engine Torque Model
The PCM uses a airflow, fuel and thermal efficiency and heat based model of torque.
- Inertia Factor: This is an engine inertia factor that is used to estimate torque required to accelerate/decelerate the engine.
- Fuel Qc Factor: This is the constant used to represent the Heat Of Combustion (Qc) in the torque model.
- MBT Torque Filter: This is the filter coefficient used to filter the calculated Mean Best Torque (MBT).
- Transfer Case Ratio: Transfer case ratio used in 4WD applications to calculate torque values when in 4WD low range.
- Accessory Torque: This is the model of accessory torque load on the engine (excluding AC compressor when engaged).
- Friction Torque: This is the model of friction torque loss within the engine.
- Friction Torque Multiplier: This is a multiplier on the friction torque value at various oil temperatures.
AC Compressor Torque
The AC compressor places a large and variable load on the engine when engaged. The PCM has a complex model of AC Torque load including inertia effects and ramp in/out when the AC clutch first engages. The AC torque calculation is also used to calculate the Idle AC Airflow compensation for IAC/ETC control during idle.
- Torque vs. AC Pressure: This is the torque loss of the AC compressor versus AC Pressure.
- Torque vs. IAT: This is the increase in AC torque loss due to inlet air temperature.
- Inertia Torque: This is the model of inertia torque load for the AC clutch when it engages.
- On Hold Time: Time to hold Inertia Torque before ramp out begins when AC clutch first engages.
- Inertia Torque Airflow Ramp: This controls the ramp out rate of AC inertia torque once the On Hold Time expires.
- Off Hold Time: Time to hold AC torque before decaying to zero when AC clutch is disengaged.
- Torque Reduction: Maximum amount of torque reduction that the AC can request.
AC Bump Torque
This is the transient model of AC torque load when the AC clutch engages and disengages.
- Delay: Time delay between commanding the AC on and the compressor loading up the engine.
- Ramp In: Ramp in rate for AC Compressor torque.
- Ramp Out: Ramp out rate for AC Compressor torque.
- Duration Max: Maximum duration for transient torque model ramp out. After this time AC torque will be set to zero when AC disengages.
- Reset Limit: If AC torque loss delta is less than this the adaptive idle cells will be reset to zero.
- ETC% Max: Maximum amount of extra ETC throttle position the AC airflow can command.
- On Delay: Delay before retarding spark when the AC engages.
- Off Delay: Delay before retarding spark when the AC disengages.
- max Spark Retard: Maximum spark retard the AC transient can request.
- Spark Off Delay: Delay before ramping spark out when the AC disengages. After Off Hold Time expires.
Delivered Torque PWM
The delivered torque PWM is used in various applications. eg. for some Holden vehicles it is used to control the fuel pump voltage.
- Stall: commanded PWM % when stall protect is activated.
- Shift In Progress: commanded PWM % when a shift is in progress.
- Normal Minimum: Minimum allowed PWM %
- Minimum Factor: Factor used to calculate PWM minimum PWM %.
- Fail Condition: PWM % applied to when torque management failure conditions are detected.
Stall Protect
- Enable RPM: If RPM drops below this them Stall Protect PWM % will be commanded.
- Delta Gain: Used for calculating RPM derivative factor to determine if engine stall is likely.
- Disable Factor - Hi: If RPM derivative factor is above this multiplied by current Desired Idle RPM then stall protect will disable (if enabled).
- Disable Factor - Lo: If RPM derivative factor is below this multiplied by current Desired Idle RPM then stall protect will disable (if enabled).
Last edited by AJT_LBA; Jan 13, 2022 at 11:52 AM. Reason: got more info regarding to post