Why does the Mercedes-Benz C-Class air conditioning not cool when idling?
2 Answers
The most common fault for air conditioning not cooling during idling is refrigerant leakage in the air conditioning system, leading to insufficient refrigerant, which causes the air conditioning to fail to cool. Method to check for refrigerant shortage: Observe through the sight glass on the dryer tank. When the air conditioning is operating normally, if continuous bubbles appear in the sight glass, it indicates insufficient refrigerant. If bubble flipping occurs, it means the refrigerant is severely lacking and needs to be replenished. Solution: The solution is to add refrigerant along with fluorescent dye. After driving the vehicle for a period, use a dedicated UV lamp to inspect the air conditioning system. If there is a leak point, it will glow. Then, repair or replace the leaking part or component.
I've dealt with similar issues before. When the air conditioning in a Mercedes-Benz C-Class doesn't cool at idle, it's usually due to insufficient power for the AC system at low engine speeds. The most common causes are insufficient refrigerant or leaks, especially in older vehicles where rubber hoses tend to deteriorate. It's also important to check if the AC compressor belt is loose - if the belt slips at idle, it won't be able to drive the compressor. Fan issues are also critical, such as blocked fan blades or motor failures, which can cause unstable AC pressure when engine temperature rises. If all these seem normal, there might be an electrical fault like a blown fuse or short circuit in the control circuit. I recommend taking it to a professional shop as soon as possible to test system pressure with gauges. Don't delay too long as it might affect the entire cooling system, especially since the problem becomes more apparent at idle.
