Mercedes-Benz W140 air conditioning refrigerant leak
500 S
W140 A/C does not cool, how is a refrigerant leak located?
If the system pressure is zero, the refrigerant has leaked out. The leak is looked for with UV dye, which can be seen in the engine bay and under the car, or with a nitrogen flush and a leak detector. The typical leak point is the evaporator.
Why did the nitrogen test not find the leak?
A nitrogen test mainly shows whether the system holds pressure, and it does not always reveal a small leak. A vacuum test can also be inconclusive. Then the leak is looked for with refrigerant and UV dye.
What if the evaporator leaks?
The evaporator is inside the dashboard, so replacing it requires a lot of disassembly and is a big job. Also check the dryer: the outlet pipe of a clogged dryer is clearly colder than the inlet pipe.
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