How to diagnose car AC problems (AC Diagnostics)

AC Diagnostics. There could be conditions when you may not be getting the amount of cool air you need from your car AC. And that is the time when you have got some issues in your car AC system and needs to be fixed.

Due to that fact, the car AC has lots of attachments and connections; you will have to figure out the damage or the fault in multiple steps to see where the problem actually is.

So, in case you want to see what has happened to your AC and what you should you do to fix it properly, you must start right from the first step that is necessary, start off your AC.

Starting your AC and check the air flow

In order to check if your car AC has some issues, you must first check its condition by turning it on. You will have to start your car, set the AC to the Hi position, temperature set to the max cold and turn on the AC.

Notice if your AC is throwing in enough air. You can check it with the help of your hand in front of the venting AC window. If the AC isn’t throwing enough air, then it could be the fault in the venting system, like the fan, the blocked venting system, mode door etc.

You can check the positioning of these components with the help of your car manual.

In case the air flow is ok, you should get to the next step.

Check the temperature

You can put a thermometer into the AC vent and see what the temperature is. If there is no cool air coming in spite of the fact the air flow is high, then you should be checking out the AC system itself. For this, you will have to turn off the car and get to the engine for checking in detail.

Check the compressor clutch

In the start, the first thing that has to be checked is the switch that connects the compressor to the system. If the compressor clutch is not turning on, then it could be the fault there.

Turn on the car and see if the compressor is turning on or not, if not you should check the switch itself and see if it is working or is lost.

In case the switch is working and the compressor has no issues in there, move on to the next thing, which is the refrigerant in the system.

Check for the refrigerant in the system

To check if the AC system has the correct level of refrigerant in it, you will need to check the pressures using pressure gauge using the manifold valve attached to the system.

For this, you will have to attach the smaller hose on the low side which is in blue, while the high side is red and is bigger in size. After that, you should check for the PSI shown on the gauge. If the gauge shows zero Psi when the engine is off, it means you have no refrigerant in the system.

If the reading has maximum Psi showing that it is overly charged. The optimum PSI should be 20-30 on the low side and 200-300 PSI on the high side, meaning that the system is properly charged.

So, if any deviation is there, you should check for the leakage in the system.

For this, you may have to put in some UV dye from the low side into the system and within some minutes you will see with the help of a UV light, where the damage actually is.

In this way, you can replace the faulty component or repair the damage properly to make sure the refrigerant in the system remains at its optimum level.


These are some of the ways you can diagnose any kind of anomalies in your car AC system. You can figure out the issues if you can check on all aspects in a careful manner, so that you don’t miss nay part.

In order to make sure you are checking on the system properly, you must be taking of the things with the help of the car manual as you will know the components more easily as compared to exploring it blindly.

Leave a Reply