How to Replace Your RV’s Air Conditioner

Replacing Your RV’s Air Conditioner isn't that hard

By FMCA

Your RV’s air conditioner(s) lead a tough life. On the roof, they are subjected to the hottest heat that the sun can dish out. They also can be damaged by tree branches when the RV is maneuvered into a tight campsite, and they just love to pick up moisture that can lead to rust. Then add in the constant vibration and pounding from the road…eek!

Like any component in an RV, especially those with movable parts, air conditioners don’t live forever. Eventually, you will have a failure. Minor items, such as starting capacitors, can be replaced, but the A/C unit itself is generally not serviceable. 

Fortunately, air conditioners aren’t all that hard to replace. You’ll need a few basic tools, some reflective foil tape, and some caulk. The hardest part is getting the new unit up on the roof.

Background

Air conditioners are designed to fit a 14-inch-square hole in the roof. That is the industry’s standard roof vent size, which makes replacement easy. Some units drop the air straight through the roof and ceiling directly into the RV’s interior; in others, air passes through ducts before entering the RV’s living areas. 

However, the air is ducted, both system types use the same 14-inch-square hole in the roof, and the air conditioner is secured with four mounting screws. Power generally is run through the ceiling to the opening.

Removing the Old RV A/C Unit

1. First, switch off the circuit breaker that supplies the 120-volt-AC power to the air conditioner so that it is safe to perform work. Set the thermostat to the “off” position, too. 

2. Next, remove the existing unit, starting with the fiberglass cover. Remove the four screws that hold the cover in place.

3. In most RV air conditioners, electrical connections and components are inside the cool air plenum to help keep them cool as well. To disconnect these, remove the sheet-metal cover from the plenum. The plenum joints may be taped; if so, use a utility knife to cut the tape at the joints. 

4. Disconnect the 120-volt-AC wires. Most likely, you will see the entire control box connected to the thermostat using two wing nuts. Remove the two wing nuts, and put the control box down into the plenum to get it out of the way. There may also be a temperature sensor probe inserted into the evaporator coil that can be removed.

5. Some units have a diffuser in the ceiling. The diffuser must be removed from the interior ceiling, and then the four bolts that hold the air conditioner to the roof must be removed. If there is no diffuser and your RV has a ducted ceiling instead, you will likely see screws installed from the A/C unit and tapped into the steel tube roof trusses.

6. Scrape off any old caulk from the screws, remove the screws, and slide the old A/C unit out of the way.

7. Once the old unit is removed, thoroughly clean the rooftop area.

Installing the New RV A/C Unit

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1. Once the new unit is up on the roof, maneuver it into position. This may require two people to ensure proper placement of the unit on the gasket.

2. Next, cut the foil tape and remove the screws from the new unit. This allows the sheet-metal cover to be removed to provide access to the front mounting holes, as well as the wiring.

3. On most new units, there is a foam gasket designed to compress and seal the area around the access hole so that water cannot enter the RV’s interior. Set the new unit in place and mark the location of the existing mounting holes; to match them, drill into the new air conditioner’s baseplate. (On a design without ducts, that would not be necessary, because the four bolts run right through the access hole in the roof.) 

4. To finish the mount, install the four screws, taking care not to overtighten and distort the base. (Overtightening can lead to warping, which can cause leaking, excessive vibration, and fan and/or compressor noise.)

5. Apply a dab of caulk over each of the four mounting screw heads.

6. Retrieve the control box from the access hole in the roof plenum, reconnect the wiring, and place the temperature probe into the evaporator core. 

7. Attach the control box to the sheet-metal cover with the two wing nuts, and reinstall the cover. After all of the sheet-metal screws are in place, cover the seams with a new roll of foil tape. 

8. Before reinstalling the cover, switch the circuit breaker back on and test the unit. 

FMCA RV Club delivers RV know-how to its members. Learn more at www.fmca.com.

This information is for educational purposes. FMCA shall not be responsible nor retain liability for RVer’s use of the provided information. Prior to making any RV service decision, you are advised to consult with an RV professional. 

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