What Are the Reasons for Slow Air Conditioning Cooling in BMW 5 Series?
3 Answers
The reasons for slow air conditioning cooling in BMW 5 Series may be due to the air conditioning compressor not working. The specific reasons are as follows: 1. Lack of refrigerant in the air conditioning system or the refrigerant pressure switch detecting low pressure or switch failure: Connect to BMW's specialized computer to read the vehicle's fault code: 009C77IHKA indicates a current fault in the coolant compressor. Check if there is a lack of refrigerant and whether the pressure switch data stream is normal. 2. Air conditioning compressor failure: Check if there is a lack of refrigerant and whether the pressure switch data stream is normal. Verify if the signal power supply from the control unit to the compressor, 6.98V, is within the normal range. 3. Air conditioning control unit failure: Check if the signal power supply from the control unit to the compressor, 6.98V, is within the normal range. 4. Air conditioning function switch failure: During the inspection of the resistance of the air conditioning compressor control coil, it was found to be open (standard value range: 10-16Ω). After removing the compressor from the vehicle, the wiring harness was measured to be normal, but the resistance of the control coil remained open. 5. Air conditioning system wiring harness open/short circuit fault.
The air conditioning in this BMW 5 Series cools down slowly. I've encountered similar situations before, and there are usually several reasons. First, insufficient refrigerant levels—if not replenished over time, it leads to low system pressure, causing the compressor to malfunction when the AC is turned on, reducing cooling efficiency. Second, the fan speed is inadequate—if the cooling fan spins too slowly or gets stuck, heat can't dissipate, and the AC struggles to cool effectively. Third, the AC filter is severely clogged—excessive dust and debris hinder air circulation, naturally slowing down cooling. Fourth, the compressor is aging—internal component wear reduces startup efficiency. Fifth, issues with the electronic controller, such as a faulty temperature sensor or loose wiring, can cause system misjudgments. If you encounter such problems, avoid DIY fixes—it's best to visit a 4S dealership for a comprehensive inspection with professional equipment, as high-end systems like BMW's aren't easily fixed with minor repairs. Regularly cleaning the radiator while driving may help prevent major malfunctions.
My BMW 5 Series also had the issue of slow air conditioning cooling a few days ago, which was absolutely torturous to drive in hot weather. Later, I found out the reason was quite simple: the cabin air filter was completely clogged like a sieve, hadn't been replaced for over a year, and the accumulated dirt was blocking the vents, resulting in reduced airflow and naturally slower cooling. Also, daily driving habits affect it too. For example, turning on the AC immediately after the car has been baking in the sun means the system has to cool down from a hot state, so it definitely takes some time. Additionally, settings matter—I once accidentally set the temperature to maximum and ended up blowing hot air for a long time. Keeping the recirculation mode off also lets hot air mix in, slowing down cooling. I recommend cleaning or replacing the filter every six months—it's low-cost and saves a lot of hassle. Don't rush the AC when starting it; wait for the system to stabilize. If the problem persists, check for refrigerant leaks, which is common in older cars.
