RV Air Conditioner Evaporator Coil Cleaning

We bought our motorhome used. It has two roof top Dometic 13,500 BTU air conditioners. The one in the bedroom had a slight musty smell. Turns out it had no filter on the air plenum intake. I disconnected shore power, went on the roof, and removed the 4 screws holding the cover in place. I still couldn't see the evaporator core clearly, so I removed the 4 screws holding the heat strip assembly, and set it to the side. The issue was easy to see.

The picture doesn't show how clogged the fins were. The dust was wet from condensate, creating a medium for nasty things to grow.	I bought a cleaning kit from Amazon. The flat nylon brush was completely ineffective in cleaning the fins. The bristles were too soft.
The metal comb brush had more potential, but all the fingers were glued together with laquer (I'm guessing). This was the cause of some negative reviews.	With finger pressure alone, I pulled the fingers apart.
Now the fingers were separated, I gently combed the fins from the bottom of the evaporator core upwards, pulling clumps of dirt and dust from the fins. The fingers of the brush slide between the fins on the coil. This also straightened some bent fins.	I then sprayed the residual dirt with a product designed for this process. Note, this is NOT corrosive, and technicallly doesn't need to be rinsed.
The old garage towel I stuffed in the gap below the coil prevented the cleaning solution from falling into the motorhome. You can see the dirt being lifted from the coils.	After the foaming action stopped, I gently rinsed the coil with a spray bottle filled with water. This is the result. That blue color is the original color of the evaporator coil. I had replaced the front A/C unit, and this was the color of the new coil.

The unit was put back together. I had my wife go in the RV and perform the olfactory (smell) check. We were both amazed the odor was completely gone. This was a really easy fix, and the materials weren't expensive. After the job was done, I installed an air filter in both A/C units. They don't have the filtration quality of a home A/C filter, but will certainly help the buildup of dust over time.

These are the products I used for this project:

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