Zoned 90+ furnace, been chugging away for 10 years. Cust just had A/C clean and check a few weeks ago. Now it's making loud whistling noise when the A/C runs. I go there and find the blower wheel just impacted with dirt. We pulled apart and cleaned her EAC (which they seem to be neglecting) but no one looked at the blower. After cleaning the wheel (no pic of wheel, sorry) I decide to look up at the secondary heat exchanger:
About a half hour later it looked like this:
It stopped whistling too! I can understand not looking at the secondary HX on an A/C check, but the blower should've been pulled with a wheel that nasty.