hot air slow, cold air fast...???
 

when i select cold air (1997 w140, lcd style controller) i get plenty, a veritible gale at full tilt.

if i select hot air (all as manual control, either by pressing the hot button on the dash, or by putting temp to HI) and increasing fan speed to max, i get very little air flow. Its hot, as you would expect, just very low flow rate.

It cant bre the filter, as air gets in when cold, and re-circ mode makes no difference. Re-circ in cold is fine. its almost like the hot radiator in the system is blocked...

any ideas?

can it be a vac operated flap not opening right?

I have the exact same problem on a 95 sclass 140? DId you figure it out or get feed back?