How to clean cooling fins on already installed AC unit?

Question

I just installed my window AC unit and then opened it up to discover that the cooling fins have quite a bit of dust caked on it. The dust looks sort of like papier mache and is sticking to the fins (a vacuum isn't pulling most of the dust off). I think this happened last year when I wasn't able to clean the filter soon enough and a lot of dust got through and got stuck to the condensation on the fins.

How can I clean this without removing my AC unit? Because of some undesirable features of the windows in my apartment, taking out and putting back in the AC unit is quite a laborious and time-consuming process. I've used foam cleaner before, but only when the AC units weren't installed so that I could hose them down. Are there foam cleaners I can use on an installed unit without making a mess?

Answer 1

I will usually use a cheap paint brush to work the dirt loose then use the vacuum. You may need to cut the bristles down to make the brush stiffer. They do make no rinse coil cleaner but usually only commercially available. Garden type air sprayers work well for rinsing the coil without making a mess. The coil should drain to the outside if it is installed right.