I have a 20 year old air handler in my basement. The air filter sits against a panel of tightly spaced metal fins right before the coils. I noticed the fins were caked with dust/dirt maybe mold. I took an old toothbrush and scrubbed between the fins as I held a vacuum up to the area. It got a lot of crud out, but the area is still generally dirty.
Is there some cleaner that I can use to scrub the area that is non-toxic and won't harm the metal (and is easy to use)?
I've had two guys come out and do checkups of the system and even though those services always seem to mention "cleaning" neither would clean the area/coils. What type of service (short of an entire duct cleaning) would take care of cleaning out the air handler and coils? I tried taking out some screws and removed some panels to open things up, but it looked like it would take more undoing than I was comfortable with to get behind the metal fins to the actual coils.