Today’s quick tip is to clean your air conditioner’s evaporator coils during your spring shakedown and your fall winterization routines. 

Why an Air Conditioner Evaporator Is Important

The evaporator is the star of the show. The air conditioner throttles warm refrigerant through an expansion valve or orifice into a low-pressure liquid inside the evaporator tubing. When this liquid vaporizes, it absorbs heat from the ambient air. This air is drawn from and returns to the interior of your RV. Pressurized by fans, the moving air passes through the cold evaporator coils, loses some of its heat (and humidity) to the refrigerant, and returns to your RV about 15-20 degrees colder than it left.

In other words, any time your air conditioner is in operation, air is flowing across your evaporator coils. Air contains moisture, dust, aerosolized oils, and other contaminants. Clean coils are effective coils, so all air conditioners have some kind of filter that should be inspected and either washed or replaced every 2-4 weeks. 

Dirty Coils Can’t Cool Effectively

But the filter is just your first line of defense. Over time, grime will still collect on your evaporator coils.

• The more you run your air conditioner, the faster grime will collect.
• The dirtier your interior air – if you smoke, have pets, or cook on the stovetop – the faster the grime will collect.
• The less you maintain your filter, the faster the grime will collect.

Grime on evaporator coils acts like an insulator. Heat can no longer easily pass between the warm interior air and the sub-freezing evaporator coils. Your air conditioner no longer cools as effectively or as quickly; ice dams begin to form on your evaporator coils; your compressor feels incredibly hot to the touch. No bueno.

>>> READ MORE: RV Air Conditioner Not Blowing Cold Air? 5 Easy Troubleshooting Tips

How to Clean Your RV Air Conditioner Evaporator Coils

The solution is simple: Clean ‘em off! You can buy a can of an air conditioner evaporator coil clean at just about any hardware store. It’s a foaming detergent that eats away oils and dust.

It’s kind of a dirty job, and you’ll need a wet/dry vacuum to clean up your project site. If you have a rooftop air conditioner, you’ll need to clean the air conditioner from the topside, so be prepared to spend 14-45 minutes on your roof. (Technically, you might be able to clean the coils from the underside if you remove the distribution box, but access is normally so limited that it’s not worth the hassle). 

1. Turn off power to the air conditioner via the 20-amp circuit breaker.
2. Remove the air conditioner shroud and evaporator cover (sheet metal or foam) to access the evaporator coils.
3. Spray the detergent cleaner on the coils. Let it sit for 5 minutes, then use a coil brush to wipe down the coils. Always brush in the same direction as the fins! (up and down, not left to right).
4. Rinse the coils with warm water from a spray bottle. Use compressed air or a wet/dry vacuum to (mostly) dry them.
5. Repeat the steps if the coils are extra dirty.
6. Clean the drip pan as best you can so the dirt doesn’t fall into the air plenum and doesn’t clog the pan weep holes.
7. Wait 30-60 minutes for the air conditioner to dry before restoring power and turning on the air conditioner.

P.S. While you’re up there, clean off your outdoor condenser coils as well! It’s the very same steps 🙂

>>> READ MORE: Here’s Why a Ducted RV Air Conditioner Is a “Most Wanted” Feature!

Cleaning RV Air Conditioner Evaporator Coils: Helpful Hints

• Don’t use a pressure washer; you’ll damage the sensitive metal fins on the coils. You may need a few different brush sizes to get into all the nooks and crannies. 
• If you used a lot of cleaner, you might want to rinse off your roof and sidewalls, too. These detergents can be rather harsh, and they can dull fiberglass gelcoat. 
• Some cleaners market themselves as “no-rinse.” The theory of operation is that you simply spray the cleaner onto the coils, work the detergent through the fins with a brush, and then condensation that forms on the evaporator (like a cold beer can on a hot summer day) when the air conditioner is running will naturally drip-rinse the coils. This theory works if your coils just need a light cleaning, but it doesn’t work if you’ve abandoned them for years. 

Here’s a tech tip from my alma mater, the National RV Training Academy.