How to Diagnose a Faulty Air Conditioning System Faster and Easier
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Trying to diagnose the exact cause of a non-working air conditioning system can be frustrating and time-consuming for most mechanics. With the few components that make up the air conditioning system on modern trucks, cars, and SUVs, there are virtually dozens of potential mechanical or electrical defects that can cause an air conditioning unit to not work inside a vehicle. However, as with any other mechanical problem, there are a few tips and processes that any mechanic can follow that will speed up the process of diagnosing and repairing an air conditioning system faster and easier than before.
Below are a few tips that can help a mechanic of any level or experience find the root cause of most air conditioning problems that vehicle owners in the United States suffer from.
Start with a diagnostic scan
If the vehicle was manufactured after 1996, it is likely that most of the reported issues are available for download from the vehicle's ECM. Virtually every vehicle system is monitored by sensors and connectors that transmit real-time data to the vehicle's engine control module; this includes the air conditioning system on most modern cars, trucks and SUVs. Thus, the best way to start any diagnosis is to download any error codes stored in the car's ECM using a digital scanner.
Most mechanics invest in having the best tools to perform repairs efficiently. However, when they use a high quality scanner that can download all the error codes, the process of finding the root cause of what is not working properly in the car becomes much faster.
Continue physical inspection of the air conditioning system.
Once the mechanic has completed the digital scan and found all the error codes, these findings usually lead him to a specific part or part. However, before you dive into the engine bay and take off the parts and details; it's a good idea to complete a physical inspection of the system. As with a test drive, the mechanic gets a real-time view of the problems customers are facing.
Here are a few steps to consider when performing a physical inspection of the air conditioning system in any vehicle:
- Turn on the air conditioner while driving.
- Turn the AC switch to the fresh air position (this will ensure there is no air recirculation, which can lead to misleading results).
- Make sure the AC switch is in the maximum position.
- Once the mechanic has set up the A/C system for monitoring, they should listen, feel, and smell for any symptoms that indicate problems with certain A/C components.
Listen: By listening to the AC system when it is fully turned on, the mechanic can determine where problems are occurring. Noises such as squealing or clanging may indicate a problem with the engine or air conditioning compressor. It could also indicate a problem with the cabin filter if it sounds like the air conditioning system is struggling to push air into the cabin.
Feel: By taking the time to feel the air blowing into the cab, the mechanic can also pinpoint other mechanical problems. If the air is warm, this usually indicates a problem with the A/C system, including a low coolant level, or a problem with the compressor. It is also important to feel the air pressure that it supplies to the cabin. If the pressure is low, this is most likely due to clogging of the ventilation system; for example, filters or the vents themselves. It may; and often causes many of today's problems with AC systems.
Smell: By smelling the air that circulates in the vehicle, the mechanic can also determine if there is a coolant leak or if the cabin air filter needs to be replaced again.
Full inspection under the hood
After downloading the error codes and completing a physical inspection of the vehicle's AC system, it will be important for any mechanic to perform an inspection under the hood. During this check, a good mechanic will do the following:
Look for any coolant leaks. Closed AC system does not allow coolant to pass through; so if the air is warm it is most likely caused by a coolant leak. Repair the leak, then recharge the system.
Check for freezing. If you notice during the physical inspection that the air was cool but then turned warm, this could be due to excess moisture inside the A/C lines, which will cause the compressor to freeze.
Check for vacuum leaks: Many air conditioning systems rely on vacuum pressure to operate effectively.
Most modern AC system problems can be easily diagnosed when a mechanic completes the above process of diagnosing a system problem.
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