This list of symptoms is not exhaustive and the possible causes of the problems is not exhaustive. There may be other symptoms not included. Also, for any symptom there may be other causes than those suggested below. 

A/C symptoms and causes are often inter-mixed and difficult to completely diagnose without the use of specialized equipment, tools and knowledgeable technicians. 

This list is not guaranteed, warranted nor is it complete. Use at your own risk. Blend Air assumes no responsibility or liability for actions of anyone relying on this information for any purpose. Use of this information is at your own risk.

Safe Practices

When trying to collect information about symptoms it may be necessary to turn on the engine and listen for sounds as the a/c settings are changed while you are inside of the car.

• Always place the transmission in Park. 
• Always set the parking brake. 
• Always place safety blocks on the ground before and behind the wheels to prevent rolling.
• Never reach your hand into the engine compartment while the engine is running.
• Never wear loose clothing, jewelry, or long hair that may get caught in engine components. 
• Never connect any gauges, hoses, pressurized Freon cans, or electrical tools to any part of the a/c system or engine unless you have studies, understand and comply with the safety guidelines provided by their respective manufacturers. 
• Never use any hand tools to perform diagnosis or maintenance work on the auto a/c system or the engine unless you have studied, understand and follow the safety guidelines of their manufacturer or the vehicle manufacturer.
• Always turn off the engine when doing a visual inspection of the a/c system with the hood open. 

Blend Air assumes no responsibility or liability for actions of anyone relying on this information for any purpose. Use of this information is at your own risk. 

Squealing, especially when starting the car or sudden increases in engine speed indicate a compressor or serpentine belt. Constant squealing at all speeds can indicate a loose or worn belt, bearing failures in the clutch or compressor.

Low pitch grinding noise from the compressor or clutch can indicate a failing compressor. 

Clicking or ticking noises can indicate a fan. 

Hissing noises during operation can indicate problems with internal pressures. A sudden burst of hissing, with or without a gas or odor that is followed by no cooling sometimes indicates a burst pressure line or hose or a failure in a hose seal. 

To collect some helpful information, start the car using safe practices. 

While the engine is running at idle, transmission in Park and parking brakes set, Turn the system on and off and observe differences in the sound. Try to isolate the noise to one of the components. These could include: the engine belt that drives the compressor clutch, the compressor clutch, the compressor, the fan inside the car. If the sounds are heard only when the car is moving, then it could be caused by loose air ducts, or baffles or vents. Unusual, loud or grinding noise from the compressor or clutch generally indicates and predicts a failure.

Noises when A/C is not  in Operation while engine is running

Check that the sound is coming from the clutch and disappears when turning on the a/c. 

Fan motors in the engine compartment often continue to run after the engine has been turned off because they have been designed by the vehicle manufacturer to keep running to help cool the engine and components.

Compressor belt might not be present or be too loose. 

A/C clutch is usually electrically operated and if it is not engaged, it will not turn the compressor. 

Internal problems  in the compressor may cause the compressor to automatically shut off to protect internal parts. This problem usually requires a trained technician. 

Freon may have leaked from the system at many possible places: Hose seals, hoses, hose connectors, any of the connectors on components such as drier, evaporator, condenser, compressor, compressor seals my be deteriorated. Leaks can be located with a leak detector. 

Some parts-houses sell cans of leak detector that can be installed into a failed system and will show where the leak is by a red or bright colored dye. Be sure to follow Safe Practices and the manufactures safety guidelines. After finding a part that leaks, it must be replaced or repaired and the system must be flushed, evacuated and then re-charged.

Vents or outlets could be held in a closed position or have been blocked with some material such as a paper towel or facial tissue, or even debris left by animals