Automotive Air Conditioning

A/C Problem Quick Check

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Here are a few common symptoms and possible causes.  Use this information at your own risk. BlendAir disclaims liability for any use, inappropriate use or non use of  this information.  

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.

Follow Safe Practices 

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. 

Noises when A/C is in operation Noises can be caused by fans, by belts, by internal valves as they deal with pressure differences, and by the compressors. 

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

 

When driving but not using the a/c, noises related to the a/c are usually from the a/c clutch. Grinding, and in some cases a metallic banging could mean that the compressor clutch has loose parts either internally or externally. 

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

Noises from A/C when engine is turned off Occasionally, on some vehicles, there may be a mild hissing sound after the engine is turned off. This usually indicates a normal situation in which high pressure and low pressure portions of the a/c system are equalizing. 

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.

Poor Cooling A/C Systems can only drop temperature from the outside a limited number of degrees if they are working in good condition. Check that the condenser in front of the radiator is not clogged( you would probably also  be having engine-heating problems in this case). It is remotely possible that airflow at the evaporator inside the car is blocked. It is possible that mold or mildew can collect in the evaporator inside the car. Another possibility is a low charge in the A/C system due to a slow leak. The charge pressure can be checked out with special A/C gauges by a technician. Also see 'No Cooling' below.
No Cooling Blower Fan inside the car may not be operating.

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.

Fan in passenger compartment will not blow air. Check for a blown or missing fuse, disconnected fan wiring, a broken switch, power wires disconnected from the fan motor. Also if the fan had been making noise and stopped, that could mean that the fan motor has worn out.
Cooling is erratic This can be caused by failing pressure switches or heat sensing switches in the system, by blockages and high pressure due to internal contamination, or faulty computer sensors. Another possibility is an intermittent short in the a/c control knobs.
Keep losing engine belt from A/C Incorrect belts being used 
Incorrect pulleys or compressor clutch. 
Incorrect Compressor or compressor configuration. 
Pulleys or clutch are not seated correctly causing misalignment and unusual belt wear on one edge and ultimately breaking.
Compressor can become frozen or locked-up and not turn. This can happen gradually or suddenly. A sudden lockup will usually result in a broken belt and possible other engine damage. 

 

Seems too cold Internal failures of the compressor and valve are possible causes. 
This can occur when too high of a pressure is building up inside the system. Sometimes a system will suffer a catastrophic failure when pressures are too high for too long a period.
Cool airflow is coming from only one or two outlets. Air ducts inside the car, under the dashboard can be disconnected or damaged.

Air baffles or doors inside the air flow ducts can be inoperative, stuck or broken. Dampers and baffles that are used to redirect airflow to different vents in some models.

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

Heavy dark Oil deposits around A/C compressor and fittings Dark heavy oil collected around a system connection usually means a leak of both Freon and oil. (The a/c system contains a several ounces of special purpose charge-oil for internal lubrication). Charge-oil leaking from a connection, o-ring seal, or hose fitting collects on the exterior surface and dirt will collect and stick to the oil giving a dirty appearance.
Engine performance bad when A/C is operating. This can be caused by an un-tuned engine, an engine suffering from poor maintenance, or an engine whose compression is falling due to high mileage. Another possibility is the compressor binding. Reasons for the compressor to bind include binding on the shaft due to other damage or wear, or too high a pressure in the system. Another possible cause is failing or faulty computer sensors or computer which fails to adjust timing and fuel mixtures to handle a slightly larger engine load.
 
 

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