Driving on a hot day in a vehicle with a malfunctioning air conditioning is annoying and even dangerous if the heat is really intense. Diagnosing why your air conditioner isn't working helps you figure out if it's a problem you can fix yourself or if you need to see a mechanic. Also, if you know the cause of the malfunction, the mechanic is less likely to take advantage of the situation.
Steps
Part 1 of 3: Collect Initial Information
Step 1. Turn on the air conditioning while the car is running
The air conditioner does not work properly with the engine off. To make a diagnosis it is better to set it on "fresh air" and not on the "recirculation" function; make sure that the air comes out of the central dashboard vents and that the air conditioner is on.
- Start with the fan on full.
- If the car has a "Max AC" setting, select it.
Step 2. Pay attention if you hear strange noises coming from the system
These could indicate a compressor problem that needs to be repaired or replaced.
Step 3. Feel the air coming out of the vents
You need to figure out if it's cold, room temperature, or warm. Also check if it is initially cold and then warms up over time or if the temperature is intermittent.
Step 4. Check the air pressure
Set the fan to maximum and minimum and make sure the air pressure changes accordingly with each change.
Step 5. Smell the air coming out of the vents
If there are any abnormal smells, there may be a leak or the cabin filters need to be replaced.
Step 6. Check the fuses
Refer to the maintenance manual to understand where the fuse box is located in your car; it could be under the hood, in the trunk or even in the pedal area on the driver's side. A broken fuse could be the cause of the air conditioning malfunction.
Part 2 of 3: Diagnosing Air Flow Problems
Step 1. Check all vents
Make sure that the air comes out of the one you have selected, switch from one to the other to understand if the system respects the commands of the knob.
- If you select a different nozzle but the air flow always remains the same, you may have a problem with the ducting system. This requires replacing the selectors inside the dashboard (the "doors" that determine the direction of the air flow).
- Selectors are also called switches.
- Sometimes an air conditioning system with a selector problem works normally, however the air flow is directed incorrectly, for example towards the engine compartment instead of the passenger compartment.
Step 2. Check the cabin air filter
This is especially important if you smell strange or have noticed a decrease in blood pressure on occasion. You should be able to notice any accumulation of dirt or debris.
- Sometimes a heavily clogged filter will interfere with the airflow pressure and its replacement is a relatively simple and inexpensive operation.
- The car's manual should contain all the instructions for changing the cabin filter. If not, do some research online by typing the words "replace cabin air filter" followed by the model and year of your car (for example "replace Fiat Punto 2008 cabin air filter").
Step 3. Check for fan motor problems
The easiest way to do this is to turn on the heat. If the airflow is weak even when set at high temperatures, then the fan motor may be broken.
- The fan motor may have a transistor problem if it blows air only at maximum settings but not at minimum.
- Unfortunately, mice and other small rodents sometimes build their own nest in the ventilation pipes and are caught by the fan when the car kicks in. A loud noise accompanied by a bad smell when you turn on the fan could indicate this problem.
Part 3 of 3: Diagnosing Air Temperature Problems
Step 1. Locate the front of the air conditioning condenser
It is usually located in front of the radiator. If you notice any leaves or other dirt, remove them and clean the area.
Step 2. Check under the hood to inspect the compressor clutch
If the air pressure is normal but comes out very hot, the problem may lie with the compressor. Check with a simple visual check that the clutch is engaged. The compressor is located at the front of the engine, inside the cowl.
- To check the compressor clutch, start the car and activate the air conditioning.
- The supercharger looks like a small engine with a large wheel at one end. The wheel (which is the compressor clutch) should turn; if this does not happen, you have found the cause of the malfunctioning air conditioning.
Step 3. Check the compressor belt tension
This element should be tight; if it appears loose, you need to replace it.
Step 4. Inspect the cooling system for leaks
One of the most common problems is a lack of refrigerant; since the air conditioning circuit is of the "closed" type, only a leak can lower the fluid level.
- Look for oily residues on or around the pipes that connect the various elements of the air conditioning system. If present, they indicate a refrigerant leak.
- You can use an electronic leak detector that is capable of sensing even the smallest amounts of refrigerant.
- There are some kits that employ a dye, a UV lamp, and goggles to find leaks.
- If you spot a liquid leak, you should go to a professional for repairs right away. Replacement parts may also be required as many items cannot be patched or fixed.
Step 5. Check for frostbite
If the system initially blows cold air but freezes after a while, there may be a freeze. An excess of air and humidity can (literally) freeze some components of the air conditioning.
- Frost can also be caused by an over-saturated accumulator.
- Turn off the air conditioning and wait for the ice to melt to fix the problem temporarily.
- If this is a recurring problem, you will need to drain the system and clean it with a vacuum pump.
Warnings
- Wear safety goggles and work outdoors so fumes don't build up and get over your respiratory system. When handling chemicals like Freon never touch your eyes or mouth. Wear long-sleeved clothing and gloves if possible.
- Do not add any coolant unless you are sure the level is low. This is because an excessive amount can severely damage the system.
- It is always best to consult a professional to carry out repairs on the vehicle.
