I had this problem with odor coming from the heat-A/C vents in my 2014 Equinox as well as my current 2017. Complained to the dealer about the 2014 but had no resolve nor could find anything as it's one of those intermittent problems. Haven't complained about the 2017 as I suspected that I would get the same results. In the 2017 it didn't start for approximately after 24,000 miles - just guessing at the date and mileage. It doesn't happen regularly and no difference between A/C and heat. My 2017 has 48,000 miles currently. The smell is hard to describe. Not sure if it's an antifreeze smell or something other. Do not notice any loss of coolant. Would be nice to know what the problem is. It's not a pleasant odor either.

This car has a definate odor when the AC, or the heat, is turned on, not every time though. I took it to the dealer, complained, and when they returned it to me, said it was tree sap ( from where I park my car) that had gotten inside the vents under my wipers, and gave me a spray bottle of deodorizer to spray in there when I smell it again. First off, there isn't one tree located ANYWHERE near my car where I park it. Second, the smell is intermittent, and it doesn't matter if it is the AC, or the heater. It only stinks when the heat, or AC is initially turned on, not while it is running, and the blower is turned up or down. I have lung cancer, and I DON'T need to be smelling this stinky odor, or some spray that is meant to mask it. I paid my good money to buy this vehicle, and I am really upset that I should have to put up with this!! It isn't a moldy smell like I have had heard someone else complain about, this smells more like chemicals. I will be taking it back to the dealer again to complain, but I feel like it's almost useless.