Air conditioner only blows out through the top windshield vents when in high medium or low settings through the top windshield vents

The mode selection is done through a series of air doors that are operated by vacuum. When there is either a partial or total loss of vacuum, the system will default to either defrost or on some vehicles, heat. Acceleration can also have an effect on the doors for the same reason.

Look under the hood for a small black plastic hose coming through the firewall. Follow it to the vacuum source looking for any breaks, cracks or leaks. Also follow any other lines that branch off because they may go to a vacuum reservoir (storage tank) and a leak there will cause the same problem. Using a vacuum gauge to determine if you have full vacuum at any given point is the best way to find it. You can cut into the line anywhere and splice it back together with a piece of vacuum hose. Find the broken line, you found your problem.

I have followed and replaced almost all hoses under the hood coming out of the firewall. I took out the storage tank located behind the battery I checked it for leaks and found none. Could the vacuum problem be inside, under the dashboard? Earlier in the week I took out actuator to see if gears were broken, but they were fine. Maybe I knocked something loose? I do remember when this problem started when accelerating that did affect where the air conditioner would blow out of.