Where -exactly- is the check valve that maintains vacuum for the A/C duct flapper? When I firewall the throttle, I lose so much vacuum the flapper shuts, cutting off my airflow. Also, no matter what position the flapper is in when I shut the car off, vacuum leaks and the flap falls to the shut position. Also, please remind me of the operation of the thermal 3-port vacuum switch in the coolant distribution pipe: 1. Describe the different modes of operation @ different temps. 2. 1 line goes to the vacuum advance solenoid. 3. 1 line goes to the intake nipple for a vacuum source. 4. 1 line goes ???? How does the charcoal evaporative cannister fit into all this? Thanks, Rich A. To address comments privately to the moderating team, please address: moderators@xxxxxxxxxxx For more info on the list, tech articles, cars for sale see www.dmcnews.com To search the archives or view files, log in at http://groups.yahoo.com/group/dmcnews Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/dmcnews/ <*> To unsubscribe from this group, send an email to: dmcnews-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/