This is Todd. I posted the famous issue with the air flow only coming out of the upper defrost vents earlier this week. I own a 1998 Bonneville SLE, and the air conditioning is now working perfectly--thanks to this loop and my few small repairs/upgrades.
After replacing the 6-port vacuum plug located on the ac programmer with 4 inch length of 7/32" rubber vacuum hoses instead, the air is now flowing through the correct vents when I tell it to. (simple pleasures in life
That repair procedure was posted earlier on this website and illustrated perfectly! --thanks!
The other thing I recommend doing is-- replacing all vacuum hoses and y-connectors under the hood. The first one and most commonly dry rotted is the one that starts from the vacuum holding canister located under the battery tray and just behind the pass side front bumper. There is the beginning of the vacuum line there that continues up to the firewall where it splits into a y-connector. One end goes to the intake manifold for the main vacuum feed, and the other travels through the firewall and into the ac programmer box (through that 6-hose plug that I eliminated by cutting it out and replacing each junction with a 4-inch length of hose. I matched up the colors and VOILA.. the ac worked again ! The 5 little nipples that the 6-port plug slides onto on the ac programmer had collapsed and didn't let the vacuum pass through to the actuators which control the doors in the duct work.
Thanks again for the help! Glad I found this website.