2003 GMC Sierra heater recirculation & defroster A/C?

[not a happy guy]

How do I turn on air recirculation for on the heater for 2003 Sierra. I bought the truck used and it seems that the computer overrides the recirc button when I move the selector to the floor position. The only way that I can keep it on is to have the selector one position to the left-(floor/vent blend). Is this just a design flaw? Did the GM engineers think that everyone is as rich as they are and keep all their vehicles in a heated garage? Did some engineer at GM think it was a good idea to have 10 degree air coming in while the truck warms up????
Also-I understand that the A/C compressor comes on to help the defroster dry the air to clear the windows faster, but why can't I shut it off? Is there any way, short of installing an aftermarket kill switch to shut it off, to re-program the computer to just use the buttons on the dash? Sometimes all it takes is a little warm air to clear the windows. Why am I forced to use the extra gas to run the A/C Compressor?
By the way, it's an SLE trim package with a dual zone climate control system.

 

[Molson02536]

How do I turn on air recirculation for on the heater for 2003 Sierra. I bought the truck used and it seems that the computer overrides the recirc button when I move the selector to the floor position. The only way that I can keep it on is to have the selector one position to the left-(floor/vent blend). Is this just a design flaw? Did the GM engineers think that everyone is as rich as they are and keep all their vehicles in a heated garage? Did some engineer at GM think it was a good idea to have 10 degree air coming in while the truck warms up????
Also-I understand that the A/C compressor comes on to help the defroster dry the air to clear the windows faster, but why can't I shut it off? Is there any way, short of installing an aftermarket kill switch to shut it off, to re-program the computer to just use the buttons on the dash? Sometimes all it takes is a little warm air to clear the windows. Why am I forced to use the extra gas to run the A/C Compressor?
By the way, it's an SLE trim package with a dual zone climate control system.

During recirculation the heater vent on the floor become the intake vent for the air to recirculate. As for your defrost question on the a/c compressor coming on, it only does it on the defrost selection to clear up the windshield.

Until you let the engine heat up, you not going to get any hot air through your vent. If your not getting enough hot air in your vent, then you may have a thermostat issue or bad circulation from your coolant crystallizing through out your cooling system.

The Dex cool has a life expectancy of 5 years and 100,000 miles. If you have never serviced your coolant system and replaced your thermostat, that's where your issue my be with your lack of heating and your going to need to have your system flushed out.

Good luck and keep us posted. Here is a post on how to flush your coolant. http://gmcowners.com/gmc-forum/showthread.php?t=15262