The problem is poor air flow, hot or cold, although all flaps and fan speed positions seem to work and the pollen filter is nearly new. Unfortunately I don't have a feel for what the fan speed should be as, when it's removed, it seems to spin properly. There's web info for the W202 LHD heater box but I haven't found any on for RHD. If the evaporator matrix is partly blocked would that reduce both the hot and cold air flow? Where would a blockage have that effect? Does this model just have poor air flow by design? What I'm trying to find out for sure is how the air gets to the fan and then through the vents, and where the heater matrix and evaporator sit in the scheme of things. Can someone point me in the right direction please?