1994 G30 front vents do not blow air
 

Hi,
Last year we had a new air cond... compressor installed. Ever since we have not had the front vents working. Only defrost & floor vents work on all settings. I currently have the cowl off and parts of the dash apart looking for vacuum leaks. I have good vacuum & no lines broken or cracked that I can see.
I have no idea how to diagnose the problem. please help....:D
The vehicle is a, 94 Chevy G30 5.7 Damon 21' C class motor home
Thanks
John

Blend door actuator?

Can you find a explode diagram of the system online?