A/C engaged on "floor" setting?

Hi all,
got a new weirdness with my '05 Impala... been using the "floor" setting a lot on the HVAC because it's finally somewhat cold here, so I
like to pump the heat to the floor to warm the cabin without frying my face off. I have noticed mileage falling off but I assumed it was due to winter gas, but today I was sitting at a light and was thinking the engine was sounding awful loud and trashy. then the noise quit. sure enough, the A/C was cycling. I determined that it is cycling on the "floor" setting and everything clockwise from there on the control (floor/defrost mix, and full defrost.) I expected it to run on defrost but it seems odd that A/C should be engaged when only the floor vents are selected. Is this an issue or is it just the way GM designed it to work?
thanks,
nate
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| Hi all, | | got a new weirdness with my '05 Impala... been using the "floor" | setting a lot on the HVAC because it's finally somewhat cold here, so I | like to pump the heat to the floor to warm the cabin without frying my | face off. I have noticed mileage falling off but I assumed it was due | to winter gas, but today I was sitting at a light and was thinking the | engine was sounding awful loud and trashy. then the noise quit. sure | enough, the A/C was cycling. I determined that it is cycling on the | "floor" setting and everything clockwise from there on the control | (floor/defrost mix, and full defrost.) I expected it to run on defrost | but it seems odd that A/C should be engaged when only the floor vents | are selected. Is this an issue or is it just the way GM designed it to | work? | | thanks, | | nate | | -- | replace "roosters" with "cox" to reply. | http://members.cox.net/njnagel |
If it is vacuum controlled you may have a leak and/or a check valve problem. My 2000 Safari had a similar problem and the shop found a small leak and the check valve was not working right either.
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Check all the control positions. Could you have left on switched on for AC while changing the air to the floor position? I don't know your particular model, but many allow the AC to be on in any vent position. It was finally somewhat cold here the past couple of mornings too. Like 3 degrees. Love those heated seats.
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According to your owner's manual:
(Floor): This mode directs most of the air to the floor outlets, with some of the air directed to the windshield and side window outlets. In this mode, the system will automatically select Outside Air. The right knob can also be used to select defog or defrost mode. For more information, see "Defogging and Defrosting" later in this section. By positioning the right knob between two modes, a combination of those two modes is selected. It should be noted, that the air conditioning compressor will be engaged unless the outside temperature is 40F (4C) or below. Recirculation cannot be selected when in Floor Mode.
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Steve Mackie wrote:

Weird. It was about 35F last night but probably over 40 degrees with the heat of the engine etc. I guess I'll just have to avoid the "floor" setting now that I know this.
nate
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Check the light on the A/C switch; if it is on, the compressor will run. Theis can be used to control humidity iside the car or turned off. Teh '05 Impala uses the same controls as my 2000, and I can turn my compressor off in any setting except defog and deice (if outside temp is above 40 degrees). Roy

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The A/C switch is off, but apparently selecting "floor" or anything clockwise from there forces it on. I can understand on defrost or a combination of floor/defrost, but why on floor only? makes no sense to me.
nate

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As stated in the manual:

It is a blend of Floor/Defrost.
Steve
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