2000 Lincoln Town Car V8 Two Wheel Drive Automatic 30,000 miles
Climate control seems to work fine until I have driven the car for 1-2 hours. Then cold air comes from the defroster vent. I can set the heat to blow on the feet. I got the info for the climate control self diagnostic test (push the 2 buttons at the same time and then the auto button) I got no codes either trying it when the system is working or when it was blowing cold air on a trip last week. The little lite moves around until every thing is lit up.
Could be a vacuum source problem. Check under the hood where the feed comes through the firewall. There should be a check valve and a resevoir on the vacuum line for the interior. Need to be sure the resevoir and the check valve are working properly and arent bleeding down vacuum