There is a really nasty, musty, smell coming from the vents and it gets worse when I turn the fan on. What could it be? - Ashley in Newmarket, Ont.
Can't be as bad as the stink coming from the vents of a car I stored a few years ago. A little rodent had taken up residence and didn't survive the winter. It cost $300 to have the entire HVAC system disassembled before they found the remains deep inside. But you have a musty smell, which is something entirely different.
First, check whether you have been using the recirculate "feature" excessively. Designed purely for use in the early minutes after start-up to heat or cool the interior more quickly, when driving through dust or pollen-laden air or behind a vehicle belching nasty fumes, recirculate can cause serious problems if used too much. Essentially you are breathing the interior air many times over and with each breath, taking more oxygen out of the air and introducing more moisture into it. I had a neighbour who had to wring out his floor mats after a leaving his HVAC system on recirculate all winter.
If you have not been abusing recirculate, look for and clear a plugged drain hose - the one that normally deposits moisture beneath the vehicle when the air conditioning is used or look for decaying leaves trapped in an intake duct. Open the hood and check along the top of the firewall behind the engine.
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