AAA Car Doctor John Paul fields a question from a Silverado owner with a strong smoky smell coming out of the air conditioning vents. Silverado owners, have you experienced this?
Q. I just purchased a 2014 Chevy Silverado pickup truck with 14,000 miles on it, I was told it was a demo. My problem is when the air conditioning is on low and turn it up I get a rancid smell like burning rubber or burning anti freeze. The only thing missing is the smoke. The dealer has looked for causes and found none. I have been what I consider patient with the Chevy dealer but I have had enough, do you have any ideas what could be causing this smell?
A. There are two things that come to mind. The first is that your truck has a buildup of mold/mildew on the air conditioner evaporator. This problem can be made worse if you tend to use the AC/heater in the “recirc” rather than fresh air setting. Chevrolet has come out with two possible repairs. The first involves coating the AC evaporator with a antibacterial cooling coil coating. The second update is to verify that the HVAC cooling fan runs after the truck is shut off. The after-blow feature dries out the moisture from the cooling coil and reduces the possibility of mildew. At the same time the shop will make sure the evaporator drain is clear to allow any condensation to drain. The second problem that I have seen from time to time is the possibility that a critter has died in the ductwork or engine compartment and the temperature causes the smell. There are also times where the HVAC system needs to come apart to look for problems.