not at all. i do it every year with the ac installed in place. place a large plastic bag under the AC.
on daraz theres a wash bag available. import from china, that bag has a drain pipe hole in it, so you catch the dirty water and drain i properly with a drain pipe.
on my dawlance unit, the card is enclosed in a plastic frame that detaches from the inner unit with a single screw. i take off the blower motor and blade connectors, and wrap a plastic bag on the control card. then pressure wash the unit. just be carefull of the degree of the water. too much pressure can damage the fins.
best if you have a short gun. Karcher is obscenely expensive.
theres a bosch aquatak, with a short gun. excellent gun on that model, short and full 360 movement