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How to Install a Dometic RV Air Conditioner: Step-by-Step Instructions

How to Install a Dometic RV Air Conditioner: Step-by-Step Instructions

There's nothing quite like the moment when you realize your RV air conditioner needs replacing—usually on the hottest day of your trip, in the middle of nowhere, with no shade in sight. I still remember the fateful day in Arizona when our 15-year-old AC unit gave its final death rattle during a 105°F afternoon. My wife looked at me with that "fix it now or I'm booking a hotel" expression that all RV spouses perfect eventually.

After two sweaty hours of research and a desperate call to a mobile RV technician (who quoted me a price that nearly caused heatstroke), I decided to tackle the installation myself. The good news? It wasn't nearly as difficult as I'd feared. The better news? I'm going to share everything I learned so your installation goes much smoother than mine did.

In this guide, I'll walk you through replacing or installing a Dometic RV air conditioner step by step.

Whether you're upgrading an older unit, replacing a broken one, or adding air conditioning to an RV for the first time, these instructions will help you complete the job with confidence. I've included product recommendations based on my experience and the feedback from dozens of RVers I've helped with similar projects over the years.

Installing Domestic RV Air Conditioner

Understanding Your Dometic RV Air Conditioner

Before diving into the installation process, it's important to understand what you're working with. Dometic is one of the most respected names in RV climate control, and their air conditioners are known for reliability and efficiency.

Types of Dometic RV Air Conditioners

Dometic offers several models, but they generally fall into these categories:

  1. Rooftop Air Conditioners: The most common type, these units mount on the roof of your RV and typically range from 13,500 to 15,000 BTU.
  2. Heat Pump Models: These units can both cool in summer and provide heat in milder cold weather, offering versatility for year-round camping.
  3. Low Profile Models: Designed with a lower height to reduce drag and improve fuel efficiency.
  4. High Capacity Models: Offering up to 15,500 BTU, these are ideal for larger RVs or extremely hot climates.

For most standard RVs, a 13,500 BTU unit provides sufficient cooling. However, if you have a larger RV (over 32 feet) or frequently camp in very hot climates, you might want to consider a 15,000 BTU model.

Key Components of Your Installation

A complete Dometic air conditioner installation typically includes:

  • The external air conditioner unit
  • A ceiling assembly (inside distribution box)
  • Mounting hardware
  • Gasket material
  • Electrical connections

Some installations may also require:

  • A new roof support structure
  • An electrical upgrade if your current system can't handle the load
  • Adapters if replacing a different brand

Essential Tools and Materials

Having everything ready before you start will save you multiple trips up and down the ladder. Here's what you'll need:

Tools:

  • Socket set and wrenches
  • Screwdrivers (Phillips and flathead)
  • Utility knife
  • Putty knife
  • Drill with bits
  • Tape measure
  • Caulk gun
  • Wire cutters/strippers
  • Ladder tall enough to access your RV roof safely
  • Non-contact voltage tester
  • Rag or towel (to cover the opening during installation)

Materials:

Optional but Recommended:


Safety First: Precautions Before You Begin

Before we get to the step-by-step instructions, let's talk safety. RV air conditioner installation involves working at height, handling heavy equipment, and dealing with electricity—a triple threat that demands caution.

Electrical Safety

  1. Disconnect all power sources: Turn off your RV's main breaker and disconnect from shore power. If you have a generator, make sure it's off and cannot start automatically.
  2. Verify power is off: Use a non-contact voltage tester to confirm there's no electricity flowing to the air conditioner circuit.
  3. Remove the AC breaker: For extra safety, remove the air conditioner breaker from your electrical panel during installation.

Roof Safety

  1. Check weight limitations: Ensure your RV roof can support your weight plus tools. Some fiberglass roofs have specific weight restrictions.
  2. Use proper ladder safety: Always maintain three points of contact when climbing. Never carry tools in your hands while climbing—use a tool belt or have someone hand them to you.
  3. Create a safe work area: Clear the roof of debris and ensure you have stable footing.
  4. Be weather-aware: Never work on the roof during windy conditions or if rain is threatening.

Lifting Safety

  1. Get help: A Dometic air conditioner typically weighs 70-100 pounds. This is not a one-person lift.
  2. Use proper lifting technique: Lift with your legs, not your back.
  3. Consider a mechanical lift: For solo installations, a mechanical lift system can help raise the unit to roof level.

Step-by-Step RV Air Conditioner Installation Guide

Step-by-Step Installation Guide

Now that we've covered the basics, let's dive into the installation process. I've broken this down into manageable steps based on my own experience and the dozens of installations I've helped other RVers complete.

Step 1: Remove the Old Air Conditioner (If Applicable)

  1. Access the roof safely: Position your ladder securely against your RV and climb up carefully.
  2. Remove the old shroud: The plastic cover over your existing unit is typically held in place by four screws or bolts. Remove these and set the shroud aside.
  3. Disconnect electrical connections: After confirming power is off, disconnect the electrical wires from the old unit. Take a photo of the wiring connections before disconnecting—this will be invaluable during reinstallation.
  4. Remove mounting bolts: Locate and remove the four bolts securing the air conditioner to the roof. These are usually accessible from inside the RV through the ceiling assembly.
  5. Remove the old gasket: Once the bolts are removed, carefully lift the old unit off the roof. Then, use a putty knife to remove any old gasket material and sealant from the roof surface. Clean the area thoroughly.

Pro tip: When I did my first replacement, I didn't clean the mounting area well enough, which led to a small leak during the first rainstorm. Take your time with this step—a clean mounting surface is essential for a watertight seal.

Step 2: Prepare the Roof Opening

  1. Inspect the roof opening: Check for any damage to the roof structure around the opening. Look for signs of water damage, rot, or cracks that might need repair before installing the new unit.
  2. Measure the opening: Verify that your roof opening matches the requirements for your Dometic model. Standard openings are 14" x 14", but some models may require different dimensions.
  3. Reinforce if necessary: If the roof shows signs of weakness, now is the time to reinforce it. This might involve adding additional support beneath the opening.
  4. Apply the new gasket: Place the Steele Rubber Products Air Conditioner Gasket Kit around the roof opening. This specialized gasket is designed specifically for RV air conditioners and provides a superior seal compared to generic materials.

A word of caution: During my installation, I initially tried to reuse the old gasket to save money. Big mistake. The old gasket had compressed over time and no longer provided a proper seal. Always use a new gasket for your installation.

Step 3: Install the Micro-Air EasyStart

Before placing the new air conditioner, I highly recommend installing a Micro-Air EasyStart Flex Soft Starter. This device reduces the starting current of your air conditioner by up to 65%, which offers several significant benefits:

  • Allows you to run your AC on smaller generators or limited shore power
  • Reduces strain on your electrical system
  • Extends the life of your air conditioner
  • Enables you to run your AC using a 2000W inverter when boondocking

The Micro-Air KIT-364-368-RT2 EasyStart Install Kit makes this installation straightforward, even for those with limited electrical experience.

  1. Identify the compressor connections: The EasyStart needs to be connected to the compressor's start winding, run winding, and common terminal.
  2. Mount the EasyStart: Find a secure location to mount the device near the compressor.
  3. Connect the wires: Following the color-coded instructions included with the kit, connect the EasyStart to the appropriate terminals.
  4. Secure all connections: Use electrical tape to insulate any exposed connections.

This addition saved my bacon during a power-restricted rally where everyone else had to choose between running their AC or using other appliances. With the EasyStart, I could do both.

Step 4: Position the New Air Conditioner

  1. Prepare the new unit: Remove the Dometic air conditioner from its packaging and inspect it for any shipping damage.
  2. Center over the opening: With help, carefully lift the new unit onto the roof and position it centered over the opening and gasket.
  3. Align with existing holes: If you're replacing an old unit, try to align the new unit with the existing bolt holes if possible.
  4. Temporarily secure: Have your helper hold the unit in place or temporarily secure it while you move to the inside of the RV.

When my friend and I installed my unit, we found that placing a small piece of wood under each corner of the AC unit helped keep it properly positioned while we moved to secure it from below. Just remember to remove these spacers before final tightening.

Step 5: Secure the Ceiling Assembly

  1. Position the ceiling assembly: From inside the RV, place the ceiling assembly (interior distribution box) against the ceiling, aligning it with the bolts from the roof unit.
  2. Start the bolts: Thread the mounting bolts through the ceiling assembly and into the air conditioner. Start all four bolts before tightening any of them.
  3. Tighten in sequence: Tighten the bolts in a diagonal pattern (like tightening lug nuts on a tire) to ensure even pressure on the gasket. Don't overtighten—just snug enough to compress the gasket slightly.
  4. Connect the electrical wiring: Following your earlier photo or the wiring diagram, connect the electrical wires from the ceiling assembly to your RV's electrical system. Typically, this involves connecting black to black (hot), white to white (neutral), and green or bare copper to ground.

I learned an important lesson during this step on my installation: label every wire as you disconnect it. I thought I'd remember which wire went where, but after a lunch break, I found myself second-guessing my memory. A simple piece of tape with a label on each wire would have saved me 30 minutes of confusion.

Step 6: Seal and Weatherproof

  1. Apply sealant: Using the Alpha Systems N102106T Low VOC Sealant, apply a generous bead around the entire perimeter of the air conditioner where it meets the roof. This specialized sealant is designed for RV applications and provides excellent adhesion and flexibility.
  2. Reinforce critical areas: For extra protection, apply Eternabond White Micro Sealant Repair Tape over the sealant at critical junctions. This tape creates an additional waterproof barrier that can prevent leaks even if the sealant cracks over time.
  3. Check for gaps: Carefully inspect the entire perimeter for any gaps or areas where the sealant might not have adhered properly.

After my first installation experienced a small leak during a rainstorm, I became almost obsessive about proper sealing. Remember: water always wins eventually, so your sealing job needs to be impeccable. I now follow the "belt and suspenders" approach—using both sealant and tape for critical areas.

Step 7: Install the Shroud

  1. Position the shroud: Place the plastic shroud over the air conditioner unit, aligning it with the mounting holes.
  2. Secure the shroud: Install the screws or bolts that secure the shroud to the air conditioner. Make sure they're tight enough to prevent the shroud from vibrating loose during travel, but be careful not to crack the plastic by overtightening.
  3. Final inspection: Once the shroud is installed, do a final inspection of your work. Check that all screws are tight and that the shroud is properly aligned.

Step 8: Test Your Installation

  1. Reconnect power: Restore power to your RV by reconnecting to shore power or turning on your generator.
  2. Reset the breaker: Replace the air conditioner breaker if you removed it and turn it on.
  3. Test operation: Turn on your new Dometic air conditioner and test all functions (cooling, fan speeds, etc.).
  4. Listen for unusual noises: Any grinding, rattling, or unusual sounds could indicate a problem with the installation.
  5. Check for air leaks: Feel around the ceiling assembly for any air leaks, which might indicate an improper seal.
  6. Monitor for condensation: During the first few hours of operation, check for any signs of condensation or water dripping inside your RV.

When I first turned on my new unit, I noticed a slight rattling sound that wasn't present in my old AC. After investigation, I found that one of the shroud screws wasn't fully tightened. A quick adjustment solved the problem. Don't ignore even minor issues—they can become major problems down the road.


Troubleshooting Common Installation Issues

Even with careful planning and execution, you might encounter some challenges during your installation. Here are solutions to common problems:

The Unit Won't Power On

  1. Check the breaker: Make sure the air conditioner breaker hasn't tripped.
  2. Verify connections: Double-check all electrical connections for proper contact.
  3. Test the outlet: If your ceiling assembly plugs into an outlet rather than being hardwired, test the outlet with another device.
  4. Check for reset button: Some Dometic models have a reset button that may need to be pressed after installation.

The Unit Runs But Doesn't Cool

  1. Check for obstructions: Ensure nothing is blocking airflow to or from the unit.
  2. Verify thermostat settings: Make sure the thermostat is set correctly.
  3. Allow break-in time: Some new units need a few hours of operation before reaching peak efficiency.
  4. Check refrigerant: If the unit still doesn't cool after 24 hours, it might need refrigerant (this requires professional service).

Water Leaking Inside the RV

  1. Check the drain holes: Make sure the condensation drain holes on the base of the air conditioner aren't clogged.
  2. Verify the unit is level: If the RV isn't level, condensation might not drain properly.
  3. Inspect the gasket: The gasket might not be properly compressed or might have shifted during installation.
  4. Check roof seal: The sealant around the unit might have gaps or might not have cured properly.

Excessive Noise or Vibration

  1. Check mounting bolts: Ensure all mounting bolts are properly tightened.
  2. Inspect the shroud: Make sure the shroud is securely attached and not vibrating against the unit.
  3. Check for debris: Foreign objects caught in the fan can cause unusual noises.
  4. Verify level installation: An improperly leveled unit can cause the fan to rub or create vibration.

Maintenance Tips for Your New Dometic Air Conditioner

To keep your new air conditioner running efficiently for years to come, follow these maintenance tips:

Monthly Maintenance

  1. Clean or replace the filter: A dirty filter restricts airflow and reduces efficiency. Most Dometic models have filters that can be removed, washed, and reused.
  2. Check and clean the condensation drain holes: These small holes allow water to drain from the unit. They can become clogged with debris, leading to water backing up and potentially leaking into your RV.

Seasonal Maintenance

  1. Inspect the roof seal: At the beginning of each camping season, check the sealant around your air conditioner for cracks or gaps. Apply fresh sealant as needed.
  2. Clean the condenser and evaporator coils: Over time, these coils collect dust and debris, reducing efficiency. A can of coil cleaner and a soft brush can help restore performance.
  3. Check all mounting bolts: Vibration during travel can loosen mounting bolts over time. Check and tighten them as needed.

Annual Maintenance

  1. Comprehensive inspection: Once a year, perform a thorough inspection of all components, including electrical connections, mounting hardware, and seals.
  2. Professional service: Consider having your air conditioner professionally serviced every 2-3 years to ensure optimal performance and catch any potential issues early.

After my installation, I created a simple maintenance calendar reminder on my phone. This small step has helped me stay on top of maintenance and has likely extended the life of my unit significantly.


Upgrading Your Installation: Optional Enhancements

Once you've successfully installed your Dometic air conditioner, consider these upgrades to enhance performance and efficiency:

Insulated Duct Covers

If your RV has ducted air conditioning, installing insulated duct covers during the off-season can prevent heat loss in winter and keep cold air from falling through the ducts when the AC isn't in use.

Smart Thermostat

Upgrading to a smart thermostat compatible with your Dometic unit can provide better temperature control and potentially save energy. Some models even allow you to control your RV's climate remotely via smartphone.

Solar Reflective Coating

Applying a solar reflective coating to your RV roof can significantly reduce heat absorption, decreasing the workload on your air conditioner and improving efficiency.


Final Thoughts: Enjoying Your Cool, Comfortable RV

Installing a Dometic RV air conditioner is a satisfying project that can save you hundreds of dollars in service fees while giving you a better understanding of your RV's systems. The process might seem daunting at first, but with careful preparation and by following these steps, most RV owners can complete the installation successfully.

Remember my Arizona story? After completing my installation and feeling that first blast of cool air, my wife's expression changed from "hotel shopping" to "impressed admiration." That night, as we enjoyed a comfortable 72°F inside our RV while the outside temperature remained in the 90s, I realized that few RV upgrades provide as immediate and noticeable an improvement to comfort as a new air conditioner.

The products I've recommended—particularly the Micro-Air EasyStart Flex Soft Starter, Alpha Systems N102106T Low VOC Sealant, Steele Rubber Products Air Conditioner Gasket Kit, and Eternabond White Micro Sealant Repair Tape—represent investments in the quality and longevity of your installation. While it might be tempting to save money with generic alternatives, the peace of mind that comes from using proven, RV-specific products is well worth the additional cost.

Whether you're replacing an aging unit, upgrading to a more powerful model, or installing air conditioning for the first time, your new Dometic air conditioner will transform your RV experience, making even the hottest camping destinations comfortable year-round.

Stay cool, and happy camping!


About the Author

I’m Bill Rowell, the founder of RVupgrades.com. In 2002, I launched the business to help fellow RV enthusiasts find unique and hard-to-find products. Over the years, it’s grown to offer more than 15,000 items, with a warehouse in Eastlake, Ohio. Having owned and repaired nearly every type of RV, I bring over two decades of hands-on experience to the table. For me, this isn’t just a business—it’s a passion and a way of life that I love sharing with the RV community.

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