When you decide to tackle an RV air conditioner installation, success boils down to three key stages: meticulous prep work, safe and steady handling during removal and placement, and a secure electrical hookup. This isn’t just about bolting on a new appliance; it’s about having the right gear, confirming your RV’s roof and wiring are up to the task, and carefully following each step to ensure a leak-proof, efficient new AC for your travels.
Your Pre-Installation Game Plan and Checklist
Before you even think about climbing that ladder, remember that a good installation starts with a solid game plan on the ground. Diving into this project unprepared is a recipe for multiple trips to the hardware store and risks damaging your rig. Think of this as your pre-flight check to guarantee installation day goes smoothly, without any costly surprises.
With RVing more popular than ever, DIY projects like this are becoming common. The global market for RV air conditioners hit about USD 1.35 billion in 2024, which shows just how many of us are out on the road. And with around 0.7 million RVs sold each year in North America, knowing how to prep for a new AC install is a skill worth having.
Confirming Compatibility and Readiness
First, you need to make sure your RV is actually ready for the new unit. This goes beyond just having a 14×14 inch hole in the roof—we’re talking about structural and electrical integrity.
- Roof Support: Can the roof around your vent handle a new AC unit, which typically weighs between 70-100 pounds? Most RVs have reinforced framing around the standard 14×14 inch vent opening, but you must check for any soft spots or signs of water damage that could signal structural weakness. Gently press around the opening; it should feel firm and solid.
- Electrical Capacity: A new air conditioner pulls significant power. You have to confirm that your RV’s electrical system and the circuit breaker it’s on can handle the amperage draw of your new model. A 15,000 BTU unit, for example, absolutely needs its own dedicated 20-amp circuit.
- Power Source: Consider how you’ll power the AC. Will you be on shore power, or do you need your generator to run it? Cross-reference the wattage needs of the new unit with your generator’s output. A 13,500 BTU AC generally needs at least a 3,000-watt generator just to start up and run properly.
Pro Tip: Never assume the old wiring is good enough. If you’re upgrading from a simple fan vent to a full-blown air conditioner, you will need to run a new, heavier-gauge 120V AC wire (typically 12/2 Romex) from your breaker panel all the way to the roof opening.
Gathering Your Tools and Materials
Having everything you need within arm’s reach is a massive time-saver and prevents you from constantly climbing up and down the ladder. This is your mission-critical checklist.
Before you start, it’s a good idea to lay everything out on a tarp or blanket next to your RV. This not only keeps you organized but also prevents you from losing small screws or parts in the grass.
Essential Tools and Materials for RV AC Installation
| Category | Item | Pro Tip |
|---|---|---|
| Hand Tools | Socket Set & Screwdrivers | A ratchet set with various socket sizes will make removing the old unit’s bolts much easier. |
| Plastic Putty Knife or Scraper | Essential for carefully removing old sealant without scratching or tearing the roof membrane. Avoid metal. | |
| Sealing | New AC Gasket | Never reuse the old gasket. A new one is absolutely critical for a watertight seal. |
| Dicor Self-Leveling Lap Sealant | The industry standard for a reason. Make sure it’s self-leveling for horizontal roof surfaces. | |
| Butyl Tape | Use this around the opening before placing the new unit for an extra layer of waterproofing. | |
| Safety Gear | Work Gloves & Safety Glasses | Non-negotiable. Protect your hands from sharp edges and your eyes from flying debris and sealant. |
| Sturdy Ladder | Make sure it’s on level ground and stable before every climb. | |
| Lifting Help | A Friend (or two!) | Seriously, don’t try to lift the old unit off or the new unit on by yourself. They’re heavy and awkward. |
Once you’ve got all your tools and supplies checked off, you’re truly ready to get started. An organized toolkit is the foundation of a job well done.
Time to Tackle the Old Unit or Roof Vent
Alright, with the prep work behind you, it’s time to get your hands dirty. Whether you’re removing a tired, old AC unit or just upgrading a standard roof vent, the key here is a methodical approach and a lot of patience.
Before you touch a single screw, your first job is to kill all the power. And I mean all of it. This isn’t a suggestion—it’s the most critical safety step. Unplug from shore power, turn off the generator, and shut down your 12-volt DC system using the battery disconnect switch or by physically removing the negative battery cable. Working on wiring when you think the power is off is a dangerous gamble.
Taking Apart the Interior Assembly
First, head inside the RV. You’ll need to remove the interior ceiling assembly, also known as the air distribution box. It’s usually just held on by a few screws. Once it’s off, you’ll expose the four main mounting bolts and the electrical wiring.
Before you unplug anything, grab your phone. Take several clear pictures of the wiring from different angles. This simple step can save you from a massive headache when hooking up the new unit. Once you’ve got your photos, you can carefully disconnect the 120V AC wiring. You’ll typically see a black (hot), white (neutral), and a green or bare copper wire (ground).
A friend of mine once skipped taking photos, thinking he’d remember the wiring. He spent an extra hour troubleshooting a dead unit, only to realize he had mixed up two connections. His advice? “Label everything, photograph everything. No exceptions.”
Moving the Job to the Rooftop
With the inside bits disconnected, it’s time to head up the ladder. The old air conditioner is secured by four long compression bolts that you’ve just loosened from inside. The only thing left holding it to your roof is a stubborn, compressed gasket and layers of old sealant. This stuff can be surprisingly tough to break free.
Your mission is to break that seal without slicing up your delicate roof membrane.
- Pry with Care: Grab a flexible plastic putty knife or a dedicated gasket scraper. Stay away from sharp metal tools—they’ll tear right through a rubber or TPO roof before you know it.
- Work Your Way Around: Gently wedge the tool under the edge of the unit and work your way around all four sides. You’ll feel the old sealant start to give way bit by bit. This takes patience.
- Phone a Friend (or Two): An old RV air conditioner is an awkward beast, weighing anywhere from 70 to 100 pounds. Do not try to lift and lower this thing by yourself. Have a buddy on the roof with you to help lift it, and another person on the ground to guide it down safely.
Creating a Clean Slate
Once the old unit is off, you’ll be looking at a messy square of old butyl tape, sealant, and gasket residue around the 14×14-inch opening. Getting this surface spotlessly clean is arguably the single most important step in preventing future leaks.
Start by using your plastic scraper to peel off the bigger chunks. For the sticky residue left behind, a rag soaked in mineral spirits or a good adhesive remover will be your best friend. Don’t rush this part. The cleaner you get this surface, the better your new gasket will seal, giving you total peace of mind the next time you’re caught in a downpour.
Setting and Securing the New AC Unit
Alright, with the old AC unit out of the way and the roof surface prepped, it’s time for the main event. Let’s get that new, 80-pound air conditioner up on the roof and locked down. I can’t stress this enough: this is a two-person job, minimum. Don’t even think about trying to wrestle it up a ladder by yourself.
The safest method is with one person on the roof and another on the ground. Position a sturdy ladder near the middle of your RV, and carefully hoist the unit up to your partner on top. It’s an awkward lift, so go slow to avoid dropping the AC or scratching up the side of your rig.
Getting it Centered and Sealed
Once the new AC is safely on the roof, gently flip it over to inspect the bottom. Your new unit will have a thick, black foam or rubber gasket already attached. This gasket is your single most important defense against leaks, so its placement is critical.
Carefully lift and lower the AC unit directly over the 14×14 inch opening. The goal here is to get it perfectly centered so the gasket makes even contact all the way around the opening. Look for any bunching, twisting, or gaps—it needs to sit completely flat.
One of the most common mistakes is trying to slide the unit into place. This is a surefire way to tear or warp the gasket, guaranteeing a leak. You must lift it up completely, eyeball the position from above, and then lower it straight down. A perfectly seated gasket is the key to a leak-proof job.
Securing the Unit From Inside
With the heavy lifting done, head back inside your RV. Now you’ll use the interior mounting plate or bracket that came with the new AC to secure the whole thing. This is usually a metal frame that goes up against your ceiling, with four long compression bolts that go through it and thread right into the bottom of the rooftop unit.
When you start tightening these bolts, do it in an even, alternating pattern, just like you would with lug nuts on a tire.
- Start by tightening the front-right bolt until it’s just snug.
- Then move to the rear-left bolt and snug it down.
- Next up is the front-left bolt.
- Finally, finish the pattern with the rear-right bolt.
Keep repeating this crisscross pattern, tightening each bolt just a little at a time. This process evenly compresses the gasket on the roof, creating the critical watertight seal. Most manufacturers will give you specific torque specs or have compression markers on the gasket itself—follow their instructions to the letter. Over-tightening can warp the AC unit’s frame and damage your roof. Under-tightening guarantees a leak.
Wiring Your New RV Air Conditioner
Alright, with the new AC unit secured on the roof, it’s time to get it powered up. The electrical part can feel intimidating, but if you take it one connection at a time, it’s completely manageable. The key is to be methodical and ensure every connection is rock-solid and safe.
The main event is connecting your new air conditioner to your RV’s 120V AC power line. Looking up into the ceiling opening, you’ll see the wire you disconnected from the old unit (or a fresh one you ran). It’ll have three wires: a black one (hot), a white one (neutral), and either a green or bare copper wire (ground). Your new AC will have the same color-coded wires, making it a simple matching game.
Connecting the High-Voltage Wires
Grab your wire nuts—make sure they’re the right size for the wires—and connect each wire from the RV to its matching partner from the AC unit. Black to black, white to white, and ground to ground.
A secure connection here is absolutely non-negotiable. First, twist the bare copper ends of the matching wires together clockwise with pliers. Then, screw on the wire nut until it’s tight. Once the wire nut is on, give each wire a gentle but firm tug. If it holds, it’s a solid connection. If it slips, redo it. A loose connection is a recipe for arcing, which is a major fire hazard.
Key Takeaway: Don’t just trust the wire nut. After you’ve confirmed a tight connection, wrap each nut with electrical tape, making sure to overlap from the base of the nut onto the wires themselves. It’s a cheap and easy extra layer of security and insulation against road vibrations.
The infographic below gives you a nice visual recap of the physical steps that lead up to this crucial wiring phase.
It’s a good reminder that all this electrical work depends on a solid foundation—a properly sealed and securely mounted unit.
Installing the Ceiling Assembly
Once the main power is hooked up and the wires are safely tucked away, you can install the interior ceiling assembly. This is often called the air distribution box (ADB), and it’s the part inside your rig that directs the cool air.
Thankfully, most modern units have made this part incredibly simple. They often connect to the rooftop unit with a simple plug-in harness for the controls, a massive improvement over older hardwired models.
- Attach the Shroud: Carefully lift the main plastic shroud up to the ceiling. You’ll need to feed the control harness wire through the designated opening in the plastic as you go.
- Plug and Play: Connect that control harness plug to its matching spot on the AC unit. It should give you a satisfying “click” to let you know it’s securely seated.
- Final Screws: Line up the shroud with the mounting points on the AC unit and ceiling bracket, then secure it with the screws that came with it. Just be careful not to overtighten and crack the plastic—snug is good.
Working with 120V AC wiring isn’t something to take lightly; following proper electrical standards is essential for safety and performance. This is even more important today, as many RVers upgrade to powerful, high-efficiency units over 15,000 BTU. These units cool effectively but need a solid electrical setup to run efficiently on shore power or a generator. You can read more about trends in the RV AC market to see just how advanced these new units are getting.
Final Sealing and Testing Your Installation
With the new air conditioner wired up and the interior assembly buttoned up, you’re on the home stretch. But don’t get too excited and grab the remote just yet. These last few steps are what separate a good DIY job from a professional, leak-proof installation that will last for years.
This is all about creating a secondary weatherproof barrier on the roof and then methodically testing your work to ensure everything runs perfectly.
Applying the Lap Sealant
Your primary seal is the thick gasket you compressed earlier, but adding a secondary seal on the rooftop is your insurance policy against water intrusion. For this job, you’ll need a quality, self-leveling lap sealant made specifically for RV roofs. This sealant flows into every nook and cranny and then settles into a perfectly smooth, waterproof membrane.
Grab your caulk gun and lay down a generous, continuous bead of sealant around the entire perimeter of the AC unit’s base. You want the sealant to cover the edge of the unit and spread out onto the roof membrane, creating a solid barrier.
More importantly, make sure you completely cover the heads of any mounting hardware or screws left exposed on the rooftop. Water loves to find its way through screw threads, and a thick dab of lap sealant is the only way to stop it.
A common mistake is being too stingy with the sealant. This isn’t the time for a thin, pretty bead. You want a substantial layer that fully encapsulates the unit’s seam and all the hardware. A leak-free roof is far more beautiful than a perfect caulk line.
Once applied, give the sealant plenty of time to cure according to the manufacturer’s instructions. This can take anywhere from a few hours to a full day, depending on the temperature and humidity. Don’t rush this part.
The Moment of Truth: Testing Your System
After the sealant has fully cured, it’s finally time for the moment of truth. Head back inside your RV, restore all power by plugging into shore power or firing up your generator, and flip the appropriate circuit breaker back to the “On” position.
Now, run your new air conditioner through all its functions. This isn’t just about seeing if it gets cold; it’s about listening and feeling for proper operation. Follow this sequence:
- Fan Only: Start by turning the unit to the “Fan Only” setting. Cycle through low, medium, and high speeds. Listen for smooth fan operation without any rattling or scraping.
- Low Cool: Next, switch it over to the low cool setting. You should hear the distinct “thump” or “clunk” of the compressor kicking on within a few seconds. The air from the vents should start to feel noticeably cooler within a minute or two.
- High Cool: Finally, crank it to high cool. The fan speed will increase, and you should feel a powerful blast of cold air. Let it run like this for at least 15-20 minutes to make sure it’s cycling correctly and actually lowering the temperature inside your rig.
While it’s running, pay close attention to any unusual vibrations. A properly installed unit should run smoothly without shaking the whole RV. If you run into any trouble, don’t panic.
Post-Installation Troubleshooting Guide
Encountering a hiccup after installation is frustrating but often a simple fix. This table will help you quickly diagnose what might be wrong.
| Symptom | Potential Cause | Solution |
|---|---|---|
| AC won’t turn on at all | No power to the unit. | Check that the RV is connected to power, the generator is on, and the AC circuit breaker is in the “On” position. Re-verify your wiring connections. |
| Unit runs, but no cold air | Compressor isn’t engaging. | Listen for the “clunk” of the compressor. If you don’t hear it, power down and re-check your wiring connections, especially the compressor wires. |
| Loud rattling or vibration | Mounting bolts are loose or debris is present. | Power down the unit. Re-check the four main mounting bolts and tighten them to the manufacturer’s specified torque. Check for debris in the fan housing. |
| Water leaking inside the RV | Gasket isn’t fully compressed. | The mounting bolts may need to be tightened further in the crisscross pattern to create a proper seal. Do not overtighten. |
| Fan sounds like it’s hitting something | Debris in the fan housing. | Disconnect power. Remove the interior and exterior shrouds to inspect the fan blades for any obstructions or leftover shipping materials. |
If you’ve run through these checks and still have issues, it might be time to consult the unit’s manual or the manufacturer’s support line. In most cases, however, a quick check of your work will get that new AC humming along perfectly.
Frequently Asked Questions
Even after a step-by-step guide, questions pop up. Every RV is built a little differently, so let’s dig into some of the most common questions from folks tackling this job.
Getting these details right matters. Roughly 25% of all complaints about RV air conditioners, like poor cooling or early failure, can be traced back to a bad installation.
Can I Add a Second Air Conditioner to My RV?
Yes, but you need to do your homework first. Many larger RVs are “pre-wired” for a second unit, typically in the master bedroom. You’ll see a standard 14×14 vent that’s already framed for an AC, with a dedicated 120V wire ready to go. If that’s your setup, the job is nearly identical to a simple replacement.
If your rig isn’t pre-wired, the project is more involved:
- Check for Roof Support: You can’t just cut a hole anywhere. You need to find a spot between the roof joists that can handle the 80-100 pound weight of an AC unit.
- Run New Wiring: This is non-negotiable. You must run a new, dedicated 12/2 Romex wire from your breaker panel to the new opening.
- Confirm Your Power Service: A second AC unit is only feasible if you have a 50-amp service. A standard 30-amp system cannot handle the electrical load of two air conditioners running at the same time.
Choosing the Right BTU Size for Your Rig
Picking the right British Thermal Unit (BTU) rating is a critical decision. Go too small, and the unit will run constantly without ever cooling the space. Go too big, and it will cool the space so fast that it shuts off before it can dehumidify the air, leaving you with a cold, clammy feeling.
As a solid rule of thumb, a 13,500 BTU unit is sufficient for most RVs up to about 30 feet. If you have a larger rig, frequently camp in hot climates like Arizona or Florida, or have poor insulation, stepping up to a 15,000 BTU model is a smart investment.
Ducted vs. Non-Ducted Systems Explained
This is one area where you don’t have a choice—it’s determined by how your RV was built. You must replace like with like.
- Ducted Systems: A central rooftop unit pushes cold air through a network of channels hidden in the ceiling to multiple vents throughout the coach. If you have this setup, you need an AC and ceiling assembly specifically designed for ducted applications.
- Non-Ducted Systems: Often called “direct dump” or “chillgrills,” the air blows straight down out of the main air distribution box on the ceiling. They are simpler and common in smaller RVs or as the second AC unit in a bedroom.
If you are replacing an air conditioner in a ducted system, you must buy a ducted-compatible AC. A non-ducted unit simply will not connect to your RV’s existing vent network.
Ready to get this project done? RVupgrades.com has a massive selection of top-brand air conditioners, sealants, and every installation accessory you could need to get the job done right. Shop our collection of over 20,000 in-stock parts and get everything you need with fast, reliable shipping.
