Why is my air conditioner blowing warm air

I’m sorry to hear that your 1999-2006 BMW 3 Series air conditioner is blowing warm air instead of cold air. This can be a common problem with older BMW models, and there are several possible causes and solutions.

One of the possible causes is that your AC system is overcharged with refrigerant. This can happen if you or someone else added too much refrigerant to the system, or if the system has a faulty pressure sensor or switch that prevents the compressor from cycling on and off properly. Overcharging can cause high pressure in the system, which can damage the compressor, the condenser, or other components. It can also reduce the cooling efficiency of the system, resulting in warm air blowing from the vents.

To check if your AC system is overcharged, you can use a pressure gauge to measure the pressure at the low-pressure port of the system. The low-pressure port is usually located on the passenger side of the engine bay, near the firewall. It has a black or blue cap with an L label on it. You can connect a pressure gauge to this port and read the pressure while the engine is running and the AC is on. The pressure should be within the recommended range for your BMW model and ambient temperature. You can find this information in your owner’s manual or online¹.

If the pressure is too high, you will need to release some refrigerant from the system until it reaches the normal range. You can do this by using a refrigerant recovery machine or by carefully opening the low-pressure port valve and letting some refrigerant escape. Be careful not to release too much refrigerant, as this can cause undercharging and other problems. Also, be aware that refrigerant is a hazardous substance that can harm your skin, eyes, and lungs. Wear protective gloves, goggles, and clothing when handling refrigerant, and avoid breathing in its vapors.

If releasing some refrigerant does not solve the problem, or if the pressure is normal or low, then you may have another issue with your AC system. Some of the other possible causes are:

• A faulty compressor that does not compress the refrigerant properly or at all.
• A dirty or clogged condenser or evaporator coil that prevents heat exchange between the refrigerant and the air.
• A faulty blend door actuator that does not direct the air flow through the heater core or the evaporator core correctly.
• A defective evaporator temperature sensor that does not regulate the temperature of the evaporator core properly.
• A bad fuse or relay that does not supply power to the AC system components.

To diagnose these issues, you will need to use a multimeter, a thermometer, and a visual inspection to test each component for functionality and continuity. You can find detailed guides on how to do this online²³⁴. If you find any faulty components, you will need to replace them with new ones. You can buy replacement parts from BMW’s official website or from other online retailers.

If you are not comfortable or confident doing these tests and repairs yourself, you may want to contact a professional BMW mechanic or a certified AC repair service for help. They have the tools and expertise to fix your AC system properly and safely.

I hope this helps you fix your 1999-2006 BMW 3 Series air conditioner blowing warm air problem. If you have any other questions, feel free to ask me. 😊