97 Lumina air cond/acceleration question

Air conditioning is great accept this happens...
you have the air cranked on a hot day, you pull off a side road onto a highway and accelerate up to 55mpg, while accelerating the air seems to shut
down until you resume an even set speed again, and then it is cold.
Is this a Chevy Lumina feature to save energy when accelerating? or just a fluke? Anyone else experience this?
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If you have it "floored" (WOT) the AC compressor is told to disengage by the PCM. That eventually causes warm air, but not for a little while. What also may occur, is that because engine vacuum drops upon accel conditions the main airflow door may not be held open (because it's vacuum actuated).
So.....it depends on what you meant by "shut down" as to whether it's normal.
GW
Cammie wrote:

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normal.
By shut down I just mean that no cool air flow was coming through any more. Not sure if it switched to hot air, or just no air because it's been so darn hot here. But once speed is resumed at a smooth level, air condition is cool again.
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Thank you for your response, I do beg to differ. Until recently my Pontiac of 7 years never did that, nor did my full size Chevy Blazer before that... or I would have asked about this sooner. LOL ;)
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Cammie wrote:

Hmm... Perhaps there is something besides the compressor shutting off. All of my own cars and most of the ones that I have worked on shut off the compressor during accel. It may be that the vacuum reservoir on your vehicle is leaking and allowing the vacuum operated hot/cold door to partially release into the neutral mode during accel. During accel, there is very little engine vac to hold the door in cold mode and it depends on a vac reservoir. How to check... It will not be easy. You will need to put a vac gauge on the temp door and measure during accel. Also, the temp vac motor itself may be bad and leaking. Put a hand operated vac pump on the door motor and see if it hold vac.
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The A/C compressor will disengage at near wide open throttle, but this should not happen during normal acceleration. It might be due to vacuum leakage in the HVAC controls..
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Compressors cut off on many late model cars. I don't know if trucks are included totally. My 85 Suburban did not do it, but my 92 Lumina and 2000 Impala will on hard acceleration. Roy

shut
just a

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Here's a little trick that I use when I'm accelerating hard. I manually select vent so that the compressr still shuts off but I keep getting cool air until I switch the air conditioning back on (works on my '90 Suburban and, if memory serves me right, also works on my '02 Impala). The reason I'm not positive about the Impala is because I rarely drive it.
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Since this is what happens automatically, I don't understand how it helps to do it manually. The fan stays on regardless of the compressor actions. Roy

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The Impala does have compressor cutout, my 2000 Impala does it. Roy

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You're right, the Impala cuts out automatically. Also, while the Suburban has plenty of power, I cut off the compressor to give me a little more (so that I can merge safely on high-speed roadways). I find it difficult to merge safely in a 65 mph zone when the traffic is doing 75-90 (I guess I could do like others and just 'push' my way in). I love that Suburban and I don't plan to get rid of it - ever. I just found out recently that my Suburban gets better gas mileage than a Toyota Sequoia (sp)(12 city and 15 highway). I currently get 16-17 mpg in the city and 20 on trip (and it carries more people plus cargo).
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I know, I got rid of mine because of body rust and potential u-joint and transmission repairs facing me when I had just bought the Impala. Now I think I should have kept it and fixed it up. Oh well, hindsight is always 20/20. Roy

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It helps on the Suburban because the compressor does not cut out under acceleration.
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The Suburban should have plenty of power to not need the compressor shut down to accelerate. My 85 Suburban did fine, only time my acceleration potential was hurt was when I had 9 people in it at one time. Roy

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During the early 70's a device called the "Pass Master " was marketed, it used a vacuum switch to cut out the AC clutch during hard accelleration. I think automakers adopted this logic, and I believe that's what's happening in your car. Possibly the switch is malfunctioning, and shutting off the AC clutch too early. Try gently accellerating, a bit harder each time, and try to see if clutch kicks out during full power [ good ] or any accellerating [ not so good ]
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I don't know where it is located,but if you are talking about the air incorrectly diverting the the windshield on a long acceleration then you are looking at a faulty check valve or a leak in the vacuum system..the easiest way to check is to try changing from vent to defrost or heat after shutting off the engine..there should be enough reserve vacuum to switch the airflow over..if not you have to open the hood and find the valve, and the vacuum ball...the check valve is usually black with 3 nipples on it.2 on each end and one on the side... real cheap to replace, just hard to find sometimes...I believe in a 97 it is located on the drivers side near the back

shut
a
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