Heil Dual Gas pack. Operates well. Heat is great and air has no
However, when switched to cool cycle and air conditioning turns on...
it smells as though it is pulling air from under the crawlspace or
from a 100 year old house. (Home is 20 years old)
Switch back to heat and smell goes away. Duct work checks out fine -
no leaks in return. Coils cleaned twice... no luck. I could throw a
lot more money at this, but would rather get some advice.