I have kind of a strange prob on my 95 formula. The heater/ac vents all work fine till I step on the gas...the harder I step the less they work. At full throttle they stop completely even tho the fan's running just fine. I know it must be vacuum related but I have no clue where to start looking under the hood, or if I even need to look under the hood. Anybody else have any experience with this?

 

Not strange at all. http://shbox.com/1/4th_gen_tech2.html#HVAC_vacuum

You probably have a leak in the hose to the vacuum tank.

 

Don't know if this applies to LT1's or not, but when I was having the computer in my car (LS1) tuned, I saw that there is a setting of approx. ~3500 RPM where the AC compressor shuts off. I'd never paid attention to it before, but after the fact, I realized it's true ... have the AC going, rev the thing above ~3500 (I can't remember the exact RPM) and the vents will stop blowing cold air.

 

compressor stops but the fan still blows. its probably the vacuum thing as rpm increase vacuum drops.all the ducting works on vacuum to operate the different baffles the direct the air to different ducts

 

I've had to replace my vacuum check valve 4 times b/c they are POS plastic. This last one I have seems to be of better quality.

 

Thanks Shoebox...thats exactly the info I was looking for. You really seem to have alot of knowledge about our cars, and a great willingness to help us guys out. Thanks
And thanks for all the other feedback too guys
I can't believe all the answers I've already gotten about my bird.....awesome!!

 

I realize that ... my point was, the COLD air stops . If it's a hot day, you notice it pretty quickly that suddenly there's WARM air blowing out the vents (when you step on the gas, bringing revs up).