The brief
The C180's air-con had been losing its bite, worst when the car was sitting at idle in traffic, and the system was clicking in and out more often than it used to. On top of that the owner had topped up the refrigerant more than once. Put those together and the picture is simple: refrigerant is escaping somewhere in the loop and the air-con can't hold a full charge.
The condenser sits right at the front of the car, behind the bumper, taking the heat out of the refrigerant. Because it's first in line for road spray, salt and grit, it's also the part most likely to corrode through and spring a small leak as the car gets older. In Singapore's humidity that's a common one.
The diagnosis
We put the system on the gauges and it came up undercharged, confirming a leak rather than just a tired compressor.
With the front of the car opened up, the condenser showed a small corrosion leak at one of its tubes, the classic age failure. The rest of the loop, the lines, the compressor, the evaporator, checked clean, so the condenser was the single point of escape.
The fix is a new condenser. We also replace the receiver-drier at the same time as a matter of course, because once the loop has been opened to air it draws in moisture, and the drier is what keeps that out of the system.
The work
The remaining refrigerant was recovered properly rather than vented, the front bumper came off far enough to reach the condenser, and the old unit came out. In went a new Mercedes-spec condenser and a fresh receiver-drier.
Then the loop was put under a long, deep vacuum to pull out every trace of air and moisture, recharged with the exact weight of refrigerant and the correct oil charge, and pressure-tested to confirm it was sealed.
Last step was a check of the vent temperature at idle and on the move before the car went back to the owner.
The outcome
Cold air is fully back, at idle and rolling, and the system is holding its pressure cleanly with no need to top up.
The C180 went home with the air-con working the way it should and the leak fixed at its source rather than papered over with another regas. With the drier done at the same time, the loop is set up to stay healthy.