Buick 2004 Rendezvous Owner's Manual page 177

You may notice a slight change in engine performance
when the air-conditioning compressor shuts off and
turns on again. This is normal. The system is designed
to make adjustments to help with fuel economy while
still maintaining the selected temperature.
On hot days, open the windows to let hot inside air
escape; then close them. This helps to reduce the time
it takes for your vehicle to cool down. It also helps
the system to operate more efficiently.
For quick cool down on hot days, do the following:
1. Select the vent mode.
2. Select the recirculation mode.
3. Select the coolest temperature.
4. Select the highest fan speed.
Using these settings together for long periods of time
may cause the air inside of your vehicle to become too
dry. To prevent this from happening, after the air
inside of your vehicle has cooled, turn the recirculation
mode off.
The air-conditioning system removes moisture from the
air, so you may sometimes notice a small amount of
water dripping underneath your vehicle while idling
or after turning off the engine. This is normal.
Defogging and Defrosting
Fog on the inside of windows is a result of high humidity,
or moisture, condensing on the cool window glass.
This can be minimized if the climate controls system is
used properly. There are two modes to clear fog or
frost from your windshield. Use the defog mode to clear
the windows of fog or moisture and warm the
passengers. Use the defrost mode to remove fog or
frost from the windshield more quickly.
Use the MODE button to select the defog mode.
-
(Defog): This mode directs air to the windshield and
the floor outlets. When you select this mode, the
system turns off recirculation and runs the
air-conditioning compressor unless the outside
temperature is at or below freezing. The recirculation
mode cannot be selected while in the defog mode.
Press the defrost button to select defrost.
0
(Defrost): Pressing this button directs most of the air
to the windshield and the side window outlets, with some
air directed to the floor outlets. In this mode, the system
will automatically turns off recirculation and run the
air-conditioning compressor, unless the outside
temperature is at or below freezing. Recirculation cannot
be selected while in the defrost mode.
Do not drive the vehicle until all the windows are clear.
3-37