Why is the BMW 5 Series' warm air not hot when set to 28 degrees?
3 Answers
There are multiple reasons why the warm air in a BMW 5 Series may not be hot. Below are the related causes: Reasons why the BMW 5 Series' warm air is not hot: The buttons in the vehicle's air conditioning control area are malfunctioning. The vehicle's engine coolant is insufficient. The thermostat in the vehicle's engine is faulty. The vehicle's air filter needs to be replaced. A specific inspection is required to diagnose and resolve the issue. Precautions for using the vehicle's warm air: Wait until the vehicle's water temperature reaches one-third of the normal operating value before using the warm air. This ensures the proper functioning of the warm air system and prevents additional strain on the engine. When using warm air, avoid setting the temperature too high. Opt for the defrost mode or footwell mode. Use the second or third fan speed setting. If the vehicle has an engine auto start-stop function, disable this feature during winter. Methods for maintaining the vehicle's warm air system: Inspect the vehicle's air filter approximately every four months. If the air filter is excessively dirty, replace it immediately. When replacing the filter, consider using an activated carbon filter, which effectively removes impurities from the outside air and improves the air quality inside the vehicle.
My BMW 5 Series had a similar issue before—the heater wouldn't get warm even when set to 28°C. There could be several reasons: insufficient engine coolant, which is the heat source for the heater—if the level is low, heat won’t transfer properly. Another possibility is a faulty thermostat; if the device controlling the coolant temperature isn’t working, the coolant won’t heat up, and the heater will stay cold. A clogged heater core can also block coolant flow and cause this issue. Sometimes, the air blend door might be misadjusted or the HVAC control unit could malfunction, preventing warm air from circulating. I’d recommend first checking the coolant reservoir to see if the level is adequate—top it up if low. Then, feel the engine temperature; if it stays cool, the thermostat might be faulty. If that doesn’t fix it, have a professional inspect the system—driving without heat in winter is uncomfortable and can affect safety. Avoid DIY fixes to prevent turning a small issue into a big problem.
I've been driving a BMW 5 Series for many years, and the lack of warm air is really frustrating. It could be a coolant circulation issue, such as insufficient coolant in the engine radiator, preventing heat from reaching the cabin. Another possibility is a malfunctioning temperature control device, causing inaccurate temperature settings in the AC unit. A non-functioning fan or a stuck air vent can also prevent warm air from blowing out. I've noticed that some owners neglect minor maintenance, like not replacing the thermostat in time, leading to low water temperature. The best approach is to stop the car and feel the engine's temperature after running—if it's not hot, check the cooling system and fan. Address the issue promptly to avoid shivering while driving in cold weather.
