The case in this post is BMW air conditioner not blowing cold, we will analyze the possible causes and use a differential diagnosis method to find the cause of the car fault the car owner is currently experiencing. Check following details:
Model: BMW G12
The air conditioner was getting worse while driving, at last the A/C not blowing cold, but air volume is normal, no any relative message appeared in dash.
The A/C compressor does not work;
Icing / blocking of A/C pipes;
A/C module failure;
Engine fan failure (the engine does not have an overheating alarm, which can be ruled out).
1. Connect ISTA diagnose computer (or other diagnose scanner) with car via OBD port, read two error codes: #20A201 and #80120A, first code is air conditioning system shuts down when overpressure, second code is the charge air coolant pump runs dry.
2. First code explain that the air conditioner is protected because of excessive pressure. What causes it? We also have to analyze the trouble codes of this coolant pump in dry operation.
3. Refer to the manual of the air conditioning system of the G12 model, it is found that this air conditioning system is different from the conventional one. Conventional is wind-cooled, this is water-cooled! This kind of "coolant and refrigerant heat exchanger" in above diagrm #5 replaces the traditional condenser, which improves the cooling efficiency of the air conditioner.
4. From the above diagram #7 is the charge air auxiliary coolant pump, 3 is the engine intercooler, 2 is the evaporation tank, 1 is the water tank, and 4 is the air conditioning compressor.
5. For comparison, the following diagram shows the structure of a traditional refrigeration cycle, 13 is the condenser, which is not found on the G12.
6. From the above analysis, first look at the coolant. There are two coolant tanks. The antifreeze tank level of the engine circulation circuit is normal. This tank has a liquid level sensor. The other low-temperature cooling tank has no coolant at all. This one does not have a liquid level sensor, so there is no alarm.
7. Antifreeze is gone! After looking around the engine room, no leaks were found, so we filled the antifreeze (coolant) and started the vehicle. Test the cooling effect of air conditioner is normal.
8. Leak detected at low temperature water tank. There were obvious traces of small stones bumping at the leak. After replacing the low-temperature water tank, the test run was normal, and the air conditioning system work well.
Models are constantly innovating and changing, and we also need to continuously learn.
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