Escort weird air behavior: Please help!

Hi :(
Brief summary: 98 Escort SW, just had engine replaced recently. When I turn on the cabin air controls, there is a periodic hissing/scraping
noise (about 5 seconds on/5 seconds off) in all positions EXCEPT the "blow air from face-level vents" position. It sounds like a motor, valve or compressor is cycling off and on. In fact, it sounds like the A/C compressor is cycling. Feels like it is loading the engine down too.
Any ideas what this could be? Again: It doesn't happen when the air switch is in the off or "arrow-pointed-at-face" position one step CCW from off. But it does happen in all positions CW from off, and in both A/C positions. In the A/C positions, the "on-time" of this noise is longer.
Problem doesn't seem to happen when the engine is stone cold.
Would really love some suggestions here.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.