Under dash noise

[EdB]

I purchased a 94 1500 a couple of weeks ago to use as a daily driver.
It has a few issues that I am working out.

Next on the list is a thumping noise coming from under the dash. It sounds
like a motor turning a gear that is not meshing. It does this when the key
is first turned to start and when it is turned off. It will do this about
15 to 20 times and then stop. It is like it either meshes or times out.
It will do it sometimes while driving.

I only have a Haynes manual and the schematic shows three different
motors associated with the AC and heating system. I plan to go after it
tomorrow.

Has anyone had this problem? What did you find? Any shortcuts?

Any help will be appreciated.

EdB