Nothing ruins a summer camping trip faster than an air conditioner that stops blowing cold. You pull into a campground in Texas in July, hook up the shore power, flip the AC on, and instead of that satisfying rush of cold air, you get a rattling noise, warm airflow, or nothing at all. The worst part is that most RV AC failures aren’t catastrophic—they’re caused by worn-out parts that could have been replaced for a fraction of the cost of a new rooftop unit.
Over the years, I’ve diagnosed hundreds of Coleman Mach and Dometic air conditioners, and the failure pattern is remarkably consistent. Dirty filters reduce airflow until the evaporator coil freezes up. Failing capacitors cause the compressor to struggle on startup. Worn blower motors lose efficiency until they burn out entirely. And cracked roof gaskets let rain leak into the ceiling assembly, damaging electrical components from the outside in.
The parts I’m recommending below address every one of these common failure points. Keeping even a few of these on hand—especially the filters and hard start kit—can save you from an expensive emergency repair or a miserable night sweating in your rig while you wait for a mobile technician.
Best for: Maintaining airflow and cooling efficiency on Coleman Mach units with 8430A series non-ducted ceiling assemblies
Clean filters are the single most important factor in keeping your RV air conditioner running efficiently, and they’re also the most neglected. These genuine Coleman Mach replacement filters are specifically sized for the 8430A series Chill Grille 2 ceiling assembly, measuring approximately 15.9 inches long by 4.2 inches wide. They’re made from non-allergenic electrostatic filter fabric that captures dust, pollen, and pet dander before it reaches the evaporator coil.
What makes these worth keeping in stock is that they’re hand-washable. You can rinse them in the sink, let them air dry, and reinstall—extending their useful life through multiple camping seasons. I recommend washing them every two weeks during heavy summer use and replacing the set entirely once a year.
I had a customer last August convinced his Coleman Mach compressor was dying because the unit was running constantly but barely cooling. Before I ordered a single part, I pulled the ceiling grille and found filters so caked with dog hair and dust that airflow was restricted to a whisper. Thirty minutes of cleaning, and the AC was blowing cold like new. Those filters saved him a thousand-dollar repair bill.
Buy Coleman Mach 8430-3691 Filter Set
Best for: Dometic Duo-Therm and Brisk Air units with ducted ceiling assemblies
If you’re running a Dometic rather than Coleman Mach—and a lot of RVs built in the last fifteen years came with Dometic units from the factory—this is the filter you need. It’s sized specifically for Dometic ducted ceiling assemblies at 14 inches by 7.5 inches, and it’s the black foam-style filter that slides into the return air grille.
This filter is hand-washable and captures dust, mold spores, and pet dander to keep your interior air quality clean. For anyone with allergies traveling in an RV, keeping a fresh filter in place makes a noticeable difference in how you feel after running the AC all day. The ducted design distributes cooled air through ceiling vents throughout the RV rather than blowing it from a single point, and a clean filter ensures every vent gets adequate airflow.
I replace these on every Dometic service call as a matter of routine. The cost is minimal, and the performance difference between a clogged filter and a fresh one is dramatic—especially in rigs where the AC is ducted to three or four ceiling vents across a 35-foot coach.
Buy Dometic Ducted AC Filter
Best for: Preventing compressor startup failures, especially when running on generator power or campground circuits with voltage drops
This is the part I recommend more than almost anything else for RV air conditioners, and most people don’t know it exists until they need it. The hard start kit includes a start capacitor and a PTCR relay that gives the compressor an extra boost of energy during startup—the moment when it draws the most power and is most vulnerable to failure.
Here’s why this matters: RV campgrounds are notorious for low voltage, especially on hot summer weekends when every site is running its AC. When the voltage drops below about 108 volts, your compressor struggles to start. Each failed start attempt is called short cycling, and it generates enormous heat in the compressor windings. Do that enough times, and you’ll burn out the compressor entirely—a repair that can cost more than a brand new rooftop unit.
The hard start kit is compatible with a massive range of Coleman Mach models spanning the 46000, 48000, 6600, 7300, 7600, 8300, 8400, 8500, 8600, and 9000 series. If you run your AC on a generator smaller than 3,500 watts, or if you camp at older campgrounds where the electrical infrastructure is questionable, this kit is cheap insurance against a catastrophic compressor failure.
A full-timer I work with had his compressor fail at Glacier National Park in July—no mobile tech available for a week. After replacing the compressor, we installed the hard start kit as insurance. He’s been running it for three seasons now on everything from 30-amp campground power to a 2,800-watt Honda generator without a single startup issue.
Buy Coleman Mach Hard Start Kit
Best for: Adding electric heat capability to Coleman Mach 10 International Series AC units for shoulder-season camping
Most RV owners don’t realize their Coleman Mach air conditioner can also provide heat—if it’s equipped with the right heating element. This 240-volt heating element is designed specifically for the Coleman Mach 10 International Series and turns your rooftop AC into a heat pump alternative for those cool spring and fall mornings when you don’t want to fire up the propane furnace.
The appeal is straightforward: when you’re plugged into shore power at a campground, electric heat costs nothing beyond your site fee. Running the propane furnace, on the other hand, burns through a tank surprisingly fast during cold nights. For shoulder-season camping in the spring and fall—when nighttime temperatures dip into the forties and fifties but you don’t need heavy furnace heat—this element takes the morning chill off without touching your propane supply.
This is a specialty part for a specific model range, so make sure your unit is compatible before ordering. But for owners of the Mach 10 International Series, it’s a worthwhile upgrade that extends your comfortable camping season by several weeks on each end.
Buy Coleman Mach Heating Element
Best for: Restoring full cooling and airflow when the original blower motor has worn out or failed
When the blower motor dies, your air conditioner is effectively useless—the compressor may still run, but without the fan pushing air across the evaporator coil, you get no cooling inside the RV, and the coil eventually freezes solid. This direct replacement motor from NBK Parts fits the entire 6000 and 8000 series Coleman Mach lineup, which covers a huge percentage of the RVs on the road.
The specs tell you this is a serious component: one-third horsepower, 115-volt, dual-speed at 1,675 and 1,080 RPM, with a double-shafted design and built-in thermal protection. The dual-shaft design is important because one end drives the condenser fan on the rooftop and the other drives the evaporator blower inside the ceiling assembly. Both functions run on a single motor, which is why the whole system shuts down when it fails.
Compatible models include the 6797, 6799, 8332, 8333, 8335, 8433, 8535, 48004, 48014, 48054, 48064, 48203, 48204, 48213, 48253, 48254, 48263, and 48264—essentially every Coleman Mach AC built in the last twenty-plus years. The replacement requires a 7.5 MFD 370V capacitor, so check whether yours needs replacing at the same time.
A seasonal campground owner I’ve worked with keeps two of these motors in his maintenance shed because when a rental unit’s AC goes down in peak season, there’s no time to wait for shipping. Having the part on hand means his tech can have the AC running again in a couple of hours instead of losing rental income for a week.
Buy Coleman Mach Blower Motor
Best for: Preventing roof leaks around the AC mounting point and maintaining a proper weathertight seal
This is a part that people forget about until water starts dripping from the ceiling assembly during a rainstorm. The roof gasket seal sits between the bottom of your rooftop AC unit and the roof surface, creating a weathertight barrier around the 14-inch by 14-inch roof opening. Over time, UV exposure, thermal cycling, and the constant vibration of travel compress and degrade the gasket until it no longer seals properly.
The result is slow water intrusion that damages the ceiling assembly, corrodes electrical connections, and in severe cases can rot the plywood substrate around the roof opening. I’ve seen gasket failures lead to complete ceiling assembly replacements that cost ten times what a new gasket would have.
This Camco universal gasket fits virtually any standard 14-by-14-inch RV air conditioner, regardless of brand. It’s the kind of part you should replace any time you have the rooftop unit removed for service—and I’d recommend checking it visually once a year as part of your roof inspection. If the foam is compressed flat, crumbling at the edges, or showing any daylight when you look up from inside, it’s time for a new one.
Buy Camco AC Roof Gasket Seal
The biggest mistake I see RV owners make with their air conditioners is waiting until something breaks before paying attention to it. A fifteen-minute maintenance routine at the start of each season will catch ninety percent of problems before they leave you sweltering at a campsite. Clean or replace your filters, visually inspect the roof gasket, listen for unusual noises during startup, and check that the condensate drain is clear and flowing.
If your compressor is slow to start or makes a laboring sound before catching, the hard start kit is your first line of defense. If airflow feels weak even with clean filters, the blower motor bearings may be wearing out—you’ll often hear a high-pitched whine before they fail completely. And any time you see water stains on the ceiling around your AC, don’t ignore it. That gasket needs attention before the water reaches the electrical components.
One more tip: never run your AC with the thermostat set below about 68 degrees, and make sure the air return path isn’t blocked by furniture or curtains. Restricted return air causes the evaporator coil to ice up, which blocks airflow completely and puts extreme stress on the compressor. Keep the air moving and the filters clean, and your rooftop unit will give you years of reliable service.
Your RV air conditioner is a collection of components that wear at predictable rates, and replacing them proactively is always cheaper than dealing with a cascade failure in the middle of summer. The filters and gasket seals are low-cost items that prevent high-cost damage. The hard start kit protects your most expensive component—the compressor. And the blower motor and heating element keep the system performing at its full potential.
Stock the small items in your onboard parts kit, schedule a fifteen-minute AC inspection before your first warm-weather trip each year, and you’ll avoid the kind of emergency breakdown that turns a vacation into a headache. Your RV’s cooling system is simpler than most people think, and keeping it healthy is well within any owner’s ability.
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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