97 Lumina air cond/acceleration question

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:

"Geoff Welsh" wrote

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.

wrote

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 ;)

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.

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..

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.

It helps on the Suburban because the compressor does not cut out under acceleration.

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 ]

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).

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