Inspect the headliner for damp, stained or wet areas along the drivers side
of the headliner.
If a damp, stained, wet or suspected area is found, remove the headliner.
Refer to
Headlining Trim Panel Replacement
in Interior Trim.
Locate the damaged or blocked section of hose using a low pressure air
supply (5 psi or less). Blow through the hose to locate the leakage or blockage.