When you turn your car air conditioner on, you should feel cooler. You should not smell anything. If you do smell something, you should take care of the issue. While you may be smelling something weird and not know where it’s coming from, there are really only a few possible causes. They include:
A Dirty Air Filter
Air filters can cause the weird smell coming from your vents if the filter is not properly cleaned. The filter can collect dirt, dust mites, stagnant water or other harmful contaminants. It can result in a terrible smell every time you turn on the air conditioner. It’s a simple fix, however: change your car’s air filter.
Bacteria and Mold Growth
One of the most common reasons of a distinct, bad smell is mold growth in your air vent. Mildew smells can be caused by bacterial growth. As cars age, bacteria, fungi and mold start to grow behind the dash panel on the evaporator.
Turning your air conditioner on to maximum can cause excess water to drip into your unit, and that can cause bacteria to grow.
Make sure that your drain tube is working properly, and use an anti-bacterial treatment to destroy any bacteria growing behind the dash panel.
Antifreeze Could Be the Culprit
If your car’s cooling system smells sweet, have your unit checked immediately. You likely have a leak in the cooling system that can come from the heater core, a pipe or hose, the coolant housing unit, or the radiator.
A Gas Leak
If you smell gasoline when you turn your AC on, you could have a gas leak. You need to repair the leak if you do smell gas. Check the fuel pressure regulator, the fuel injector O rings in the engine compartment, and the exhaust system for any leaks.