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Discussion Starter · #1 ·
Greeting all,

This is my first post in this great forum. I had car accident and I had to replace damaged ac condenser that is covered by full insurance . After that I started experiencing strange ac compressor cut out (hot air comming) that occurs “somtimes” only when im slowing down or about to stop. I took it to the agency and the technician team were very friendly and did everything possible trying to resolve this issue and even they had to replace the ac condenser with new one to eliminate any possible defective ac condenser or blockage in the system. Unfortunately, the problem still exists! They have requested to leave the vehicle to discuss and share this problem with engineering department at GM. After a week they informed that there is nothing wrong with your vehicle.

Still the problem exists and I thought of sharing this problem with this forum hopping that someone had similar issue and has managed to fix it.

Waiting for your feedback.
 

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A/C condenser? am "assuming" your are referring to the condenser in front of the radiator. The Agency? Is that a dealership? Did the "Agency" replace the condenser? They discussed the problem with GM's engineering department?

This is an HVAC problem...right?

Am not jumping on U, but could you go into a little more detail?
 

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Discussion Starter · #3 ·
A/C condenser? am "assuming" your are referring to the condenser in front of the radiator. The Agency? Is that a dealership? Did the "Agency" replace the condenser? They discussed the problem with GM's engineering department?

This is an HVAC problem...right?

Am not jumping on U, but could you go into a little more detail?
Yes A/C condenser is the one in front of the radiator. Yes agency has replaced it twice.

First one after the car incident as the A/C condenser get damaged.

Second time after I was complaining from A/C cute out.

Yes car agency has discussed this technical issue with GM engineering department, but their conclusion that there is nothing wrong with my car A/C.

FYI, my A/C had no issue before the incident.

Finally, yes correct it is HVAC problem.

Hopefully, I have provided all details.
 

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OK;
Has there been gauges hooked up to the system, if so, what are the readings, engine off, engine running, fan(s), if rear a/c, on high, at idle, at 1500 rpms, compressor engaged?

What was the ambient temp.?
 

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Discussion Starter · #5 ·
OK;
Has there been gauges hooked up to the system, if so, what are the readings, engine off, engine running, fan(s), if rear a/c, on high, at idle, at 1500 rpms, compressor engaged?

What was the ambient temp.?
All what have been mentioned above have been performed by the technician team at the agency. The problem is weird! It is happening ONLY when Im slowing down and about to stop then the A/C cute off for few seconds only then engaged agin. Also, I have no problem while Im driving or even at idle for a lone time and even when the ambient temp is around 113°F the A/C work find with no issues at all.
 

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This will take 2 people.

Connect a set of gauges and mimic the situation with vehicle in park. Idle up to 1600 rpms, a/c fan(s) on high, whats the center vent temp?, what do the gauges read?, idle down 200 rpms, repeat dropping 200 rpms and taking readings until the problem appears, be sure U note the readings at that juncture and look at the a/c clutch, if engaged or not.

Need to have a R134A pressure/temp.chart and note the ambient temp.
 

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Discussion Starter · #7 ·
This will take 2 people.

Connect a set of gauges and mimic the situation with vehicle in park. Idle up to 1600 rpms, a/c fan(s) on high, whats the center vent temp?, what do the gauges read?, idle down 200 rpms, repeat dropping 200 rpms and taking readings until the problem appears, be sure U note the readings at that juncture and look at the a/c clutch, if engaged or not.

Need to have a R134A pressure/temp.chart and note the ambient temp.
I don’t have that experience to do it myself, but I’ll ask someone to help me doing it.

BTW, I forgot to tell you that we have used the OBD reader and took the car for a quick ride and the technician note down the readings when the A/C cute off and share it with engineering department at GM and their feedback was that readings are normal.

I wonder if defected A/C pressure sensor/switch could cause such an issue!!

Anyhow, thank you so much for your feedback.
 

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its almost like the computer senses a drop in RPMs and commands the AC compressor to shut off.


out of curiosity.. try this.
Get a can of throttle body cleaner.
Disconnect battery.
Access the throttle body. Spray the cleaner into the throttle body-- especially the sides where the throttle plate moves.
Use your other hand and gently spray the sides while you move the plate open and close.
Make sure the battery is disconnected for about 30 minutes.

Once this is done... put it all back together. Reconnect battery.
Start vehicle. (it may crank a little longer than usual due to the TB cleaner) but it will eventually start.
Then go for a drive with AC OFF.

then turn on AC and see if the AC issue reappears.
let us know if this corrects the issue.
 

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Discussion Starter · #9 ·
its almost like the computer senses a drop in RPMs and commands the AC compressor to shut off.


out of curiosity.. try this.
Get a can of throttle body cleaner.
Disconnect battery.
Access the throttle body. Spray the cleaner into the throttle body-- especially the sides where the throttle plate moves.
Use your other hand and gently spray the sides while you move the plate open and close.
Make sure the battery is disconnected for about 30 minutes.

Once this is done... put it all back together. Reconnect battery.
Start vehicle. (it may crank a little longer than usual due to the TB cleaner) but it will eventually start.
Then go for a drive with AC OFF.

then turn on AC and see if the AC issue reappears.
let us know if this corrects the issue.
In fact, the technician from the agency told me that they have been advised by engineering department from GM to perform throttle body cleaning, and honestly I laughed when I hear that because they haven’t explained to me as you did in your post, and I thought they are kidding as I was believing that there is no correlation between the A/C and the TB. Also, Im not sure if they have cleaned the TB and if they did have they followed exactly the same steps you have mentioned in your post. I guess your assumption about computer sensing a drop in RPMs and commands the AC compressor to shut off is most properly correct. I’ll drop by the agency and ask them to follow your steps in cleaning the TB and see if this will resolve the issue or not and keep you posted.

thank you so much again for your active participation to my post and valuable feedback .. truly appreciated.
 

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So what happens is overtime the throttle body gets dirty and the computer learns to deal with a dirty throttle body it's able to save learned parameters in memory. the battery is disconnected for some reason, this erases learned parameters. It is now back to default values. The engine is now running on a dirty throttle body but with default values and especially when you turn on the AC it doesn't know how to respond fast enough. so you turn on the AC or you come to a stop and the compressor comes on it loads down the engine and it wants to shut off so the computer realizes something's wrong and it shuts off the compressor and then the engine responds slowly and RPMs go up.... it causes a surging as the compressor turns off as the computers trying to keep the engine running .
 
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Discussion Starter · #11 ·
So what happens is overtime the throttle body gets dirty and the computer learns to deal with a dirty throttle body it's able to save learned parameters in memory. the battery is disconnected for some reason, this erases learned parameters. It is now back to default values. The engine is now running on a dirty throttle body but with default values and especially when you turn on the AC it doesn't know how to respond fast enough. so you turn on the AC or you come to a stop and the compressor comes on it loads down the engine and it wants to shut off so the computer realizes something's wrong and it shuts off the compressor and then the engine responds slowly and RPMs go up.... it causes a surging as the compressor turns off as the computers trying to keep the engine running .
Greeting rbarrios,

After your post I started reading about dirty TB and its correlation with AC problem. I came to know also that dirty/faulty Idle Air Conditioner (IAC) valve can cause A/C problem like idle rough when the A/C is on, which I don’t have currently. So, I wonder if Air Conditioner (IAC) valve is causing similar issues to what I’m experiencing now.

So, what do you think? And shall I ask the technician to check the IAC as well for possible damage.

Waiting for your feedback please.
 

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I dont know about IAC.
My experience in my other chevrolet, was cleaning the TB, disconnecting battery, and it corrected my issue
 
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Discussion Starter · #14 ·
I dont know about IAC.
My experience in my other chevrolet, was cleaning the TB, disconnecting battery, and it corrected my issue
Hello my Dear rbarrios,

Finally, I have tried your suggestion by cleaning TB then disconnect the battery for 30 min and reconnect it again. The issue improved by 70% now, but still AC disengaged for few seconds (around 15-30 sec) then kicks agin. In other words frequency of AC disengagement is less than before. So, do you think that TB need more cleaning (although it Looks like new after cleaning) or TB is malfunction and need to be replaced with new one! Any other suggestions?
 
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