Vehicle presented with a loss of refrigerant, the standard evacuation of the A/C was preformed and no gross (large) leaks were detected. Our service protocol is always recharge the air conditioning (A/C) systems with a UV test dye during any A/C service. Since the refrigerant is a gas, it is very near impossible to visually witness the leakage, other than perhaps refrigerant oil staining. The UV dye clearly shows the point of leakage, be it a hose, seal, compressor or other part. One of the most challenging components of the A/C system to diagnose is the evaporator core, located inside the dash of the car itself. As the A/C evaprorotr core is not readily visible, except by much dissembly of the dash itself, we use a three point diagnosis on these, the first part is confirming the loss of refrigerant, second, we inspect all visible components of the A/C system to eliminate any external parts, finally we inspect the drain pipes for the evaporator core, looking for telltale evidence of the UV test dye to present in the condensation run off.
Replacement of the air conditioning (A/C) evaporator core is no easy task on any car, yet alone a vehicle as complex and well engineered as a Mercedes Benz. Access to the core involves removing the center console, complete dash, steering wheel, airbag, radio, climate control head and basically stripping the car down to the engine firewall. You can see by the photos that this is no easy task. If the diagnosis is done correctly, you’ll see the evaporator core stained with the dye.