Charcole filter depends if you have the switch. The switch is properly the only easiest thing to check. Do you have the switch that turn on/off the charcole filter?? In the early 140, the hood will have series of opening near the windshield.... however in the later model, all have the opening so its not the best bet.
If you still unsure to the switch, you can go into diag. mode for the A/C module and look up from there. Which A/C module do you have?? Do you have the 3 seperate panel module or the one big LCD module. Both have been described on this board as to how to go into the diag. mode.
If you have charcole filter, your car will have 3 filters. Re-circ filter, pre-filter and the charcole filter. The Re-circ filter can be changed in 10 minutes and is inside the car under passenger dash.
The pre-filter is just before the blower which can be changed in 20 minutes. U need to open the hood, remove the BIG black thing going across left and right and u will see the pre-filter. Don't force anything, there are a few electrical and vacum connections.
the charcole..... u must remove the wiper, wiper motor and others to access it.... its costly too... not a recommended frequent item. Its also described on this board as to exactly how to do it.