heat only vents to windshield

[Mike Robbins]

When i put the blower motom switch in any position(floor,upper vent or windshield) it will only bolw on the windshield. Any suggestions, Thanks. Mike

[rajadomba]

My AC switched to the windshield with load on the engine a while ago and I eventually found out that a vacuum check valve had a hole in it. It was simple and inexpensive to replace. The vacuum lines run from the intake manifold and split off to a number of locations, one apparently the AC/heat switch. After auto parts shops couldn't help I found replacement vacuum check valves for both on my system from the US Plastics website for a few dollars each. The dealership wanted about a hundred to fix the problem...