2005 Honda Civic VP

In the past I've been dealing with smelly AC that smells like dirty socks. I've changed cabin air filter and sometimes spray some aerosol into air intake to disinfect the system. This helps but is usually short lived.

However, I found a much more effective way to clean the evaporator and that is to buy a special can of spray foam made for cleaning evaporator (Kool-It HVAC system cleaner) that comes with a little hose to shove into the AC drain plug. I did this recently and after I ran out of the spray foam, I used the little hose that it came with and sprayed some soapy water from my pressurized 1 gallon garden sprayer into the hose to get some more foamy soapy bubbles to build up in the evaporator then did a final rinse off with some less soapy water.

The AC smells like freshly laundered clothes now but it did make some noises when starting up and there is a slight whistle now that I can hear when the AC is running. All of the AC vents are open and I don't think its coming from the cabin filter area either. It sounds like its coming from down in the evaporator coil area low down below the dash.

I've pressed the button between circulate and recirculate and run the fan on high. I notice the noise when its in fresh air mode but haven't noticed it in recirculate mode. I'm wondering maybe if some of the water or spray foam I sprayed in there got something wet. Is there a fan or something down there or something electronic? What would lead to a slight whistling sound? I haven't done any long drives yet on the car but its been a couple of days already.