Missing Floor Heat 1995 318i

Finally go my car to go with a replacement DME,.. what a relief !!

Now would like to address the issue of the floor heat setting. I am able to get good powerful air-flow from the defrost setting and the vent setting, but when I rotate the setting knob to the Floor setting, I get very little air-flow.
There must be a duct door that is not opening, or closing, properly.

Any ideas on where to look to resolve this??

Thanks