Leaves, twigs and other organic matter can cause havoc with gutters on your house—and the same on your vehicle. Quite often when we open and hoods on vehicles, we see the air plenum (or called air cowl) below your windshield built up with this debris. This can cause all sorts of concerns. First, this will eventually plug your Heating / Air Conditioning drain tube. The drain tube vents all the moisture and condensation in the HVAC system. Also, you will receive less air movement from your air vents because of the clogged air plenum. So, open your hood and check the vents under the windshield. It only takes a few minutes to clean.