Automotive Air Conditioning Repair Troubleshooting Guide

On a hot summer day, turning on the air conditioner only to get warm air out is a driver’s nightmare! Don’t rush to pay a big buck to a repair shop, sometimes you can do automotive air conditioning repair yourself. This guide will help you figure out the reasons why your air conditioner is not working, and what you can fix yourself and what you should leave to a professional.

1. ❄️ Is the air conditioner actually turned on?
◦ Check again whether the AC button is pressed (indicator light is on).
◦ Is the temperature knob/setting adjusted to the lowest (blue area)?
◦ Is the air volume turned on? Are the air outlets open and in the correct direction?
◦ Hyundai models: Check the air conditioner settings on the central control screen. Is it set to “Energy Saving Mode” or “Ventilation Only” by mistake?

2. 🌬️ Is the air conditioning filter clogged? (The easiest solution!)
◦ Symptoms: The air volume is significantly reduced, and the wind feels weak even at the highest setting, and there may be a strange smell.
◦ Location: Usually behind the co-pilot glove box or near the windshield in the engine compartment (check the vehicle manual).
◦ Inspection: Take out the filter and hold it against the light to see if it is seriously clogged by dust, leaves, etc.
◦ Solution: DIY is highly recommended! Buy the corresponding model filter online and replace it easily in 5-10 minutes according to the tutorial. It is recommended to replace it once a year or every 10,000-20,000 kilometers.

1. 👂 Listen to the compressor when starting the air conditioner:
◦ When the AC button is pressed, can you hear a clear “click” sound from the engine compartment (clutch engages)?
◦ Does the engine speed increase slightly afterwards (compressor starts working)?
◦ No “click” sound/speed remains unchanged: The compressor clutch is not working! Possible reasons: circuit problems (fuse, relay, switch), severe lack of refrigerant (pressure protection), clutch failure, sensor problem.

2. 👀 Observe the condenser (in front of the water tank):
◦ Open the engine compartment and find the smaller heat sink (condenser) in front of the water tank.
◦ Check if it is seriously blocked by catkins, mosquitoes, and dirt? This will greatly affect the heat dissipation efficiency!
◦ Solution: You can try DIY cleaning. Use a low-pressure water gun or a soft brush to carefully rinse from the inside of the cabin to the outside (note! High-pressure water guns will damage the heat sink). Severe blockage requires disassembly and cleaning.

1. 💧 Refrigerant (coolant) leakage or shortage:
◦ The most common reason! System pipes, joints, and seals are aged or damaged, leading to leakage. At this time, refrigerant replacement is required
◦ Symptoms: The cooling effect gradually deteriorates until it disappears. The compressor may not start after pressing the AC (low pressure protection). A prompt may appear on the dashboard of some models.
◦ ⚠️ Important warning:
▪ Do not blindly add “leak sealant” or inferior refrigerant! It is very easy to damage the compressor, pollute the entire system, and increase the maintenance cost!
▪ Refrigerant filling requires professional equipment and technology! The old refrigerant must be recycled, vacuumed, and filled according to the exact number of grams.
▪ The leak point must be solved! Simply “adding fluorine” only treats the symptoms and not the root cause, and it will soon leak again.
◦ Professional solution: The repair shop uses a leak detector (fluorescent, electronic) to locate the leak → repair the leak (replace the seal, repair the pipeline) → recycle the old refrigerant → evacuate → add the original or compliant refrigerant (such as R134a or new environmentally friendly refrigerant) + refrigeration oil according to the standard amount.

2. ⚡ Compressor failure:
◦ Symptoms: The clutch does not engage at all (after eliminating circuit and refrigerant problems), or makes a harsh noise or shakes violently after engagement, and the compressor does not work or has extremely low efficiency.
◦ Possible causes: Internal wear and seizure, clutch burnout, coil failure, insufficient refrigerant oil leading to lubrication failure.
◦ Solution: Professional repair is required! Replacing the compressor assembly or repairing the core components is the main solution. After repair, the pipeline must be thoroughly cleaned, the liquid storage dryer/collector must be replaced, and the refrigerant and refrigerant oil must be refilled.

3. 🔌 Circuit/control system failure:
◦ Symptoms: The AC button does not respond, the compressor clutch does not engage, and the fan does not rotate.
◦ Checkpoints (some of which can be DIY for initial inspection):
▪ Fuse: Check the manual to find the air-conditioning-related fuse (may be in the car or engine compartment fuse box), and check whether it is blown. Replace the fuse of the same specification (a few yuan).
▪ Relay: Find the air-conditioning compressor relay (usually in the fuse box), and try to swap it with the relay of the same specification next to it (such as the horn relay).
◦ Complex problems: Pressure sensor failure, temperature control switch failure, air-conditioning control panel damage, line short circuit/open circuit. A professional diagnostic instrument is required to read the fault code to locate the problem.

4. 💨 Condenser fan does not rotate:
◦ Function: To dissipate heat from the condenser. Poor heat dissipation will cause excessive pressure on the high-pressure side, poor cooling effect, and even trigger a protective shutdown.
◦ Check: Start the engine and turn on the air conditioner to observe whether the fan (one or two) located in front of the condenser or water tank rotates normally.
◦ Fault: Fan motor damage, relay failure, temperature control switch problem, line failure. If heat dissipation is affected, it must be repaired as soon as possible, otherwise the compressor may be damaged.

5. 🚫 Expansion valve/throttle tube is blocked or failed:
◦ Function: Control the refrigerant flow and pressure changes to achieve cooling.
◦ Symptoms: The high-pressure tube is abnormally hot, the low-pressure tube is not cool (or frosted), and the refrigeration effect is poor. The compressor may shut down due to high-pressure protection.
◦ Solution: Professional repair! The failed parts need to be replaced, the system pipelines need to be cleaned, and the dryer needs to be replaced.

🛑 Safety warning: When should you stop and hand it over to a professional technician?1. Any operation involving refrigerant (coolant): filling, recycling, leak detection, vacuuming. Special equipment and qualifications (R134a, etc.) are required and there are risks if the operation is not done properly.
2. Disassembly and replacement of core components such as compressors, condensers, evaporators, expansion valves, etc.
3. Complex circuit diagnosis and repair.
4. The system pipeline has serious leaks or needs welding repair.
5. When you still cannot determine the cause or solve the problem after following the above steps

1️⃣ Check the settings and filter → 2️⃣ Listen to the compressor & look at the condenser → 3️⃣ Check the fuse & relay (simple circuit)
⬇️
If the problem is still not solved → Send it to a professional auto repair shop or 4S shop immediately!
Remember: Replace the air conditioning filter regularly, check the air conditioning system once a year before summer (including refrigerant pressure, clean the condenser), and perform auto air conditioner repair in time. It is the best investment to prevent air conditioning failure and keep cool!