What Causes the BMW Air Conditioning Compressor Not to Start?
4 Answers
Refrigerant being too much or too little, excessive impurities in the system, or air in the air conditioning refrigeration system. Below are the specific explanations: 1. Refrigerant being too much or too little: Both excessive or insufficient refrigerant can cause the car air conditioner to not cool. Excessive refrigerant is usually caused by overfilling during maintenance, as there is a specific requirement for the proportion of refrigerant volume in the air conditioning system. If the proportion is too high, it can affect heat dissipation, meaning more heat dissipation results in greater cooling capacity; conversely, less heat dissipation leads to smaller cooling capacity. If there is insufficient refrigerant in the air conditioning system, the amount of refrigerant sprayed into the evaporator from the expansion valve will also decrease, and the heat absorbed during evaporation in the evaporator will consequently reduce, leading to a decrease in cooling capacity. 2. Excessive impurities in the system: If there are too many impurities in the refrigerant and the refrigeration oil, it will inevitably clog the filter screen of the filter, reducing the refrigerant's flow capacity, increasing resistance, and decreasing the amount of refrigerant flowing to the expansion valve, thus resulting in insufficient cooling capacity.
I've recently researched this issue. There are typically five possible reasons why a BMW's air conditioning compressor stops working: insufficient refrigerant can trigger a protection mechanism, causing the compressor to shut down automatically; the compressor itself may be faulty, such as internal jamming or burned coils, which requires professional diagnosis; electrical system failures are the most troublesome - poor relay contact or blown fuses can prevent startup (I once had a fuse issue); pressure switch misjudgment can also lock the compressor, especially when sensors are dirty; finally, don't forget to check the AC control panel - program errors or button failures can cause command transmission failures. In such cases, it's best not to tinker blindly - having a dealership read the fault codes is most reliable, as replacing a failed compressor isn't cheap.
I've encountered situations where the car's compressor wouldn't start. The core issue often lies in the power supply chain: first, check the power relay—oxidized contacts can prevent 12V voltage from reaching the compressor; then inspect the corresponding 20A fuse in the fuse box—a blown fuse naturally cuts off power; also pay attention to aging wiring, especially in high-temperature areas of the engine bay where insulation can wear and cause short circuits; compressor control module failures are more subtle and require diagnostic tools to check data streams; another small detail is abnormal readings from the AC pressure sensor, which can trigger system protection shutdowns. It's advisable to start with the basics—test the relay and fuse first, and if that doesn't resolve the issue, proceed to a professional shop for electromagnetic clutch inspection.
BMW A/C Compressor Not Starting? Don't Rush to Replace Parts, Do These 4 Checks First: First, check the A/C panel settings - temperature set too low may trigger protection mode; Second, inspect refrigerant pressure - compressor won't operate if below standard value; Third, examine if the electromagnetic clutch can engage - start the engine with A/C on and listen for a clicking sound underneath; Fourth, use a multimeter to test power supply voltage - if not 12V, check fuses and relays. If all these are fine, there's an 80% chance it's a compressor failure. Last time I encountered this, it was due to slight refrigerant leakage causing insufficient pressure that prevented compressor startup.
