This is one of the many easy ways. The footwell flaps are interconnected through linkage from the footwell vacuum pod. Unfortunately it seems the driver 's side seems to brake leading to the great heat on the pax side but nothing on the driver's as the air pressure keeps that flap closed. The proper way to fix it would be to take the heater box out and replace the flap. If you look on EPC you can see where it is located long with the repair kit for the linkages. The weekest spot it the chain is the top of the flap where it connects to the linkage. I verified that it was indeed the top of the flap where it connects to the linkage by using a mirror to look up at the top and see a part of it rotating as the heat came on. I have to eventually repair the evaporator so I will save the repair until then and of course get two new flaps.

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Buddy Ligon
1985 300SD
1969 280SE Cabriolet