Well if the directional flaps are working and the fan is blowing then there are only two reasons for the lack of heat, the engine isn't hot enough or the heater circulation is blocked.
For the recirculation mode, after operating your dash control you will hear the damper closing therefore cutting off the incoming external air flow, after cutting off the flow u will find the cab gets warmer but may also mist up, so then u restore the external flow to clear. Use the recirculation mode if you have a/c to keep the cab as at it's coolest.
The recirculation mode on a 200 is vacuum controlled so may not work if u have an iffy vac pipe.