Ac troubles: I own two 2004 Chevrolet Silverado trucks. At least once a week and sometimes several times in one day, the two drivers side vent blow hot air while the other two passenger vents blow cold air as normal.

- Rosharon, TX, USA

Ambient outside temperature of approximately 25-degrees Fahrenheit and lower causes in-cab heater/ac control that determines where air flow will be directed (defrost/floor/dash vents/combo) to stick. Occurs around one time in five; an intermittent problem. If, after commencing driving, the windshield begins to fog over and the outlet selector is stuck in any position other than defrost, it can become impossible to see out the windshield. This has caused dangerous conditions along with requiring me to pull over until the interior of the cabin heats up, allowing the selector switch to function. Truck taken to dealer many times under warranty about this problem. At times the truck was left for several days to allow replication. For whatever reason, dealer was unable to replicate the problem thus refusing to try to rectify the problem. It appears the dealers I used (3 total) were unwilling to diagnose the potentially dangerous condition. The dealers responses were such that I was basically told that I would have to live with a potentially dangerous condition. I have learned to leave the switch set in the defrost mode when parking the truck allowing the use of the defrost mode during initial operation during cold weather. Of course, that means the A/C is operating, reducing gas mileage and the cabin takes longer to heat. If I happen to forget to leave the setting at defrost I face possible catastrophe if the windshield fogs severely while operating the vehicle. Generally, when the switching system in inoperative it takes 20 minutes of so for it to begin working again. Sure was tiresome hearing dealers escape warranty work by using the "can not replicate" mantra. This lame excuse was used with other problems. When GMC expects me to spend my dollars with them in the future I, too, shall use the "can not replicate" mantra.

- Elkhorn, NE, USA

2004 duramax will not defrost windshield or warm cab after 1 hour plus of idle operation. If windshield is scraped it fogs over when operated down the road to warm the engine. This problem, from freezing temp. And worsens as the temp. Drops. I purchased vehicle 10-30-2003 and GM service says that there is nothing wrong with my truck. Is this true that they are allowed to design and sell a vehicle in this climate that will not warm up enough to defrost the windows in such a period of time. Operation of this vehicle is neither safe for myself or anyone on the road.

- Brandon , MN, USA

Front defroster was inoperative. As a result, the heat was blocked off, causing impaired vision. 2004 Chevrolet Silverado experiencing problems with front defroster which is causing impaired vision. Dealer explained to consumer that the design of the defrost system was to prevent the winshield from cracking at the bottom.

- Hudson Falls, NY, USA