1983 300D wierd ac vent question

[rfdillon]

Folks, I have been physically disabled for the last 4 months, and when I started driving again last week, I discovered that the AC vents are acting up. I have heat coming out of the two left-most vents, and the right vents have cold air coming out of them. My wife tells me that this summer the ac came out of the two left-most vents, and heat came out of the right-most vents.
Has anyone experienced this, and do you have any suggestions as to how I might fix this? Thanks so much in advance!