Start with the fan speed turned to its highest setting. If your car has a “Max AC” setting, select that option.
When your AC is on its highest setting, the clutch on the compressor should spin with the accessory belt. [3] X Research source The compressor is a cylindrical container, usually located next to the engine. It’s the heavy lifter in your car’s AC system—it’s responsible for compressing the refrigerant and pumping it through your vents. The compressor will normally have two metal lines running into it. One goes to the radiator; the other goes to the dashboard.
If it’s really hot outside, the air coming out of your vents will probably be 50–70 °F (10–21 °C). This is normal. If it’s relatively tame or cold outside, it should be 35–40 °F (2–4 °C). If the temperature is warm or room temperature, you either don’t have enough refrigerant in the system, the refrigerant is leaking, or the compressor is broken.
If you don’t have any air coming out of the vents, you probably have an issue with your blower motor. If the airflow slows down dramatically when it’s at a higher speed setting, the problem is likely your filter. The location of your vehicle’s air filter will differ from make and model to make and model, so refer to your user’s manual to find the exact location. Usually, you open the glovebox and remove a little drawer to access the filter.
If changing the vent doesn’t change anything, you have a “blend door” problem. Get a professional mechanic to fix this one. [7] X Research source
A lot of mechanics will note that a dirty filter often causes a car to smell musty, or moldy. Radiator fluid tends to smell a lot like antifreeze, which has a slightly sweet, chemical odor.
It is possible that your cabin air filter is so blocked that it is interfering with your air pressure, and replacing it will be a relatively easy an inexpensive fix to your problem. Your car manual may have instructions on replacing the cabin filter. If it doesn’t, try searching online for “replace cabin air filter” followed by the year, make, and model of your car (for example, you might search for “replace cabin air filter for 2006 Toyota Camry”).
Turn the car off before reaching inside of the hood.
Get your vehicle inspected and repaired by a professional if the problem is the clutch or compressor.
You can buy a replacement belt yourself and pull it around all of the pulleys yourself, but this is a very easy and cheap repair for a pro. If you don’t get the order of the pulleys correct, you could end up causing damage to your engine or engine components.
If the fuse is dead, buy a replacement and simply pop it into the slot where your old AC fuse was installed. Note, if the fuse dies again, you have a wiring problem that requires a pro.
If you don’t see any leaks on the ground, you can run dye through the AC lines to identify minor leaks. Look for oily residue on or around hoses that attach AC components together. Oily spots indicate a refrigerant leak. If you do find a leak, hire a professional to repair the damage and refill your system.
Freezing can also be caused by an oversaturated receiver/drier or accumulator. If the problem is persistent, get your system to be flushed or evacuated with a vacuum pump.
