Hi, Dave,
My question is: The A/C unit smells of mold when it’s running (so bad we cannot sit in there when it’s running). I have taken everything apart from the inside (filters and ducts) and it is spotless. How do I access the drip pan? The unit is a Coleman-Mach 3. Is that accessible from the roof? How does the outer casing come apart? —Allen, 2020 Forest River Salem Cruise Lite 19DBXL
Hi, Allen,
If you have tried cleaning from the inside of the rig, you removed the air return cover and found the filter and evaporator coil. The smell most likely is coming from mold that has accumulated due to standing water in the drip pan, like you suggested, and would only be accessed from the roof.
How the air conditioner works
When the unit turns on, the fan pulls warm, moist air from inside the rig up through the air return and draws it through the evaporator fins. The coolant “flashes” and cools the air about 16-20 degrees and also draws out moisture, which should drop to the drip pan. The drip pan is slanted and the moisture should go out the drip holes. That is the condensation you see coming off the roof.
There could be mold and mildew build up on the evaporator fins, or in the drip pan if the holes are clogged. To access these components, you will need to get up on the roof and remove the outer cover or shroud. Most models have a protective metal plate over the front area that houses the evaporator fins and drip panm so this needs to be removed as well.
Clogged up evaporator fins
Below is a unit that stopped working because the evaporator fins got caked with body powder! Not only the fins are plugged, but the drip pan is also coated with flaky powder. The high amp draw ruined the compressor.
Hopefully, yours is not this bad and can be cleaned with a fungicide. There are specific cleaners for evaporator fins; however, most will not do much for mold and mildew. I recommend Concrobium® Mold Control, which can be found on Amazon here.
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Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”
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