Q. We have a 2011 motorhome that has two air conditioning units. Although we periodically wash and dry the foam filters in the units, we are getting a musty odor every time we turn it on. The odor only lasts a few minutes, but it is truly unpleasant. First we thought we may not have completely dried the filters, but that doesn’t seem like it would cause a continual problem. What can we do to get rid of this problem? — Ralph and Susan
A. The evaporator coils on your air conditioning unit are probably in need of cleaning. Dust and lint can build up on the coils even when you keep the filters clean. Since the coils condense moisture, it is a perfect environment for mold and mildew.
Sometimes spraying an aerosol disinfectant like Lysol into the inlet vents can help kill the odors, but the long-term solution is to either clean the coils yourself, or have the units cleaned by a service facility. These coils are on the inside of the air conditioning unit. They are not the condenser coils that are visible on the rear of the unit when you are on the roof of the RV.
It is also important to clean the condensation drains on the units periodically, like once a year, to ensure that the condensation water can freely flow out of the unit when it is running.
If you want to tackle the job yourself, you can read a step-by-step tutorial on coil cleaning by clicking here.
Most roof units will be similar to the ones pictured. Before you start, make sure you feel comfortable working on the roof with standard tools and cleaning supplies, and make sure the RV is unplugged from shore power when you work on the air conditioner units.