Remove 'shroud' ---that will allow you to the 'sealed' cover over the evap coil and drip pan under the evap coil
The drip pan collects the condensation that drips down from evap coil as the warm air flows thru the evap coil and cools
The condensation then drains out via drip pan drain holes..usually two/one at each end of evap coil. Condensate drains out onto roof and runs off
The drain holes get clogged with debris/slime etc condensate then accumulates getting carried over into room air discharge plenum/ducts etc and then when the fan stops the condensate overflow drip pan and leaks out thru ceiling grill.
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