on my 98 civic the A/C output to the dash and defrost/windshield decreases to about 25% output when the recirc button is engaged. when depressing the recirc it sounds like something in the dash drops, then the air flow decreases... any suggestions what could be going on and how to fix it?

 

Is just the A/C or heat aswell? Where does the noise come from? It could have something to do with the core.

 

i didn't notice it last winter when using heat and i haven't currently tried it, now that you mention it. what if it only does it on A/C?