The air vents on the passenger side of my 1996 850 do not automatically change from heating to A/C. Last fall I had to take the car to my mechanic who manually opened/closed some doors to change from A/C to heat. He told me that he did not have the diagnostics to determine what motor had to be replaced so it was easier to do it manually. Now that warm weather is approaching it is time to switch to A/C again. Any idea on what doors need to be closed/opened so I can do it myself for the short term? Also, what is defective causing this manual intervention in the first place?

You must be having the ECC system on board. Sorry i cant help much on that.