Auto Air Conditioning Troubleshooting – How to Fix your Car’s Air Conditioner

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Auto Air Conditioning Troubleshooting

One of the joys of car ownership is trying to figure out how to fix the problems that creep up over time. Knowing what is wrong and assessing whether the repair is a DIY job or you need a mechanic is important. This applies to auto air conditioning troubleshooting. Knowing what the problem is means you can either fix it or take it to someone who knows how to do the proper repair.

The first thing to understand with car AC is something called the Black Death. This refers to something that begins inside the compressor where the refrigerant is broken down.  The refrigerant in the AC unit works similarly to motor oil in an engine. It lubricates and protects the internal workings. If the refrigerant has broken down, then internal air conditioner wear starts and the compressor will be compromised. Once this happens, sharper and dirtier pieces of metal created with compressor breakdown flow through the whole AC unit, doing serious damage.

An air conditioner can rarely come back from the Black Death, so you must do AC checks regularly.

Things to Troubleshoot

Things To Troubleshoot
Photo by Olav Tvedt on Unsplash

Weak Airflow

The only thing worse than no air conditioning is weak air conditioning.

Weak airflow is barely worth having the A/C on. If you notice that your car has this issue, look at it early to avoid any further problems. You don’t want to leave it until it is something you cannot repair or it ends up costing you a lot of money.

Causes of weak airflow can be: 

  • Mold and mildew. These two nasty things can gather in the evaporator core when extra moisture is present while the air conditioner is actively cooling. If there is a buildup of mold or mildew, the cooler air will not be able to fully reach the car air vents.
  • Loose hoses. This is not a difficult fix or hard to find. If a hose has come loose there will be limited airflow. Check the blower hose that sends the air to the air conditioning blower unit.
  • Problems with the ventilation fan motor. If the fan is not working properly, the air will not flow well. Make sure it is working as it should be.
  • Make sure the seals are sealed. Check the seals on the core case, the blower housing, and the evaporator core to make sure they haven’t opened. If any of them are have then the airflow is reduced. Car A/C systems are temperamental and need full seals to work. If any seal is open, then the system will fail.

Check all these items and then decide how to proceed. You can replace seals, fans, and hoses as you are comfortable. If it is beyond your talents, then take it to a mechanic for repair.

Check out our article on A/C Recharge Costs so you can budget the repair.

Lukewarm AC

Lukewarm A/C

If your car air conditioner is not as cool as it should be then you need to find out what is going on as the problem can range from minor to something that could be a significant issue.

  • You may have a freon leak due to problems with O-rings, a seal, loose hose or other parts. The system needs to be sealed to maintain the freon content.
  • An expansion tube or the refrigerant charging hose may be stopped up. This will stop the cool air from being produced.
  • Compressor issues can be significant. If the compressor fails or a broken compressor clutch happens then your air is not going to be cool enough.
  • Blower motors and their resistors can be problematic. If either is failing or broken, then there will be little cool air.
  • Condenser and evaporators also play a part. If either has failed or is damaged, then the air will not be cool.
  • Electrical can be a problem as well. Check switches, fuses, relays, and solenoids for proper function.

All these are issues need to be checked. Once an A/C system leaks then it’s a big problem not only with the cooling of air but for keeping the system repairable. You do not want a long-time leak to affect moisture in the system and do more damage. Repair the leaks and easy access fuses but if it is a major motor or other significant A/C part then a mechanic may need to see it.

If you’ve recently charged your AC system, there are 4 reasons your AC may not be blowing cold air.

Cool To Warm AC

Cool to Warm A/C

Car air conditioners are finicky and need to be babied. Keep an eye on the system to see if issues are present that are causing warm air. Look for the following:

  • Expansion valves can be problematic. They make sure that the refrigerant goes in the proper quantity to the evaporator. If blocked, the refrigerant is stuck and will freeze the valve together.
  • The compressor clutch is not working properly. You will get hot air if the pressure in the compressor is not right. This happens when the clutch is not working in tandem with the compressor.
  • Blown fuses can be a problem. Check them and replace them as needed.

Leaks can instigate most issues. Check for leaks and repair as you can or have a mechanic fix it.

Smelly A/C

If you’re A/C smells, then try changing the air cabin filter or clean the evaporator case as it can get mold in it. Make sure the case’s drain is not blocked either.


DIY repair on your A/C is doable if you know how to find a problem such as leaks. To detect leaks, you can use a black light. Many refrigerants are mixed with dyes that show up when you use it. Simply turn off the lights, turn on your black light, and look at the system to see what appears. You can also use something called a sniffer. It finds the refrigerant compounds and can point out where a leak is.

Final Thoughts

Fixing your car’s air conditioner can be simple or complicated. Figure out what the issue is and then decide whether you can apply a quick DIY fix or it needs more professional attention. You can fix a hose, fuse, and sometimes a seal but unless you are the ultimate fixer then someone with proper tools and insight may have to look at it.

Hit a roadblock? Let us connect you with a pro.

If you’re having trouble with your car, it might be time to talk to an expert. Scanner Answers is proud to partner with RepairPal to help you find the best deals on car repair in your area. RepairPal mechanics specialize in offering high quality work at guaranteed fair prices. Find a Repair Shop or speak with an expert now Call (877) 314-1060