Tap or Click coming from Under Dash

I have 2 Lincoln TC's. Both 1998's. Both have clicking noises coming from under dash near glovebox. Taps about 15 times, then stops. Does it upon starting engine as well as stopping. 1 car did it always, the other only started doing it when I had the heater core replaced. Anyone know exactly what this noise is?:screwy:

... Anyone know exactly what this noise is?

? Exactly ? .. well you're in a much better position to see "exactly" what's up with that ticking :)
The rest of us can only give experienced guidance..

To begin with, let's determine if there's any related problems.. a few posts down there's links to Climate Control Self Testing.. this shortcut should jump there > http://www.automotiveforums.com/vbulletin/showpost.php?p=6117799&postcount=2

Put your Climate system in test mode to see if it shows any trouble codes.

Test mode will probaby indicate a blend door problem. See other blend door posts;