Dometic RV AC Not Cooling? 5 Common Fixes for Air Conditioner Troubleshooting Guide

The Straight Answer

WARNING: Always disconnect power at the electrical panel before working on AC units. Electrical components can cause serious injury or death.

Your Dometic Brisk Air rooftop AC running but only blowing warm air while the fan operates normally points to one of three main culprits: low refrigerant levels, a dirty or frozen evaporator coil, or a failed compressor. Since it worked fine last season and the fan is functioning, common causes include refrigerant leaks that may have developed over the winter months. The compressor may be trying to run, but without adequate refrigerant, it can't create the pressure differential needed for cooling. This is actually one of the more common issues we see with rooftop RV units after they've sat unused for several months.

The fact that your Dometic Brisk Air is running but not cooling suggests the electrical components are functioning properly, which narrows down our troubleshooting considerably. Unlike residential HVAC systems, RV rooftop units are sealed systems that can't be easily recharged in the field, so if it's a refrigerant issue, you're looking at either a professional repair or potentially replacing the entire unit depending on the age and condition of your system.

Breaking It Down

Let's start with understanding what's actually happening inside your Dometic Brisk Air when it's working properly. The refrigeration cycle begins when the compressor pressurizes refrigerant and sends it to the condenser coils on the outside of your unit. These coils release heat to the outside air, cooling and condensing the refrigerant back into a liquid. This liquid then travels through an expansion valve into the evaporator coils inside your RV, where it rapidly expands and absorbs heat from the indoor air that's being blown across it by your fan.

When you hear your unit running but getting warm air instead of cold, something has interrupted this cycle. The compressor might be running but not actually compressing refrigerant effectively. This could be due to low refrigerant levels from a leak, internal compressor failure, or blocked refrigerant lines. Another possibility is that the evaporator coils have become so dirty or iced over that they can't properly absorb heat from the air passing over them.

RV air conditioners are particularly susceptible to refrigerant leaks because of the constant vibration and movement they experience during travel. The connections and coils can develop small leaks over time, and even a minor leak will eventually drain enough refrigerant to prevent proper cooling. Additionally, the condenser coils on top of your RV are exposed to road debris, weather, and UV radiation, which can cause deterioration of the coil fins and refrigerant lines.

The timing of your issue - working fine last season but not cooling now - is also telling. During storage, condensation can freeze in the evaporator coils if the unit isn't properly winterized, potentially causing damage. Rodents or insects might have nested in the unit, blocking airflow or damaging components. Even dust and debris accumulation over several months of non-use can significantly impact performance when you fire it up for the new camping season.

What You Need

Before diving into repairs, you'll want to gather the right tools and supplies for proper diagnosis. Start with a digital multimeter capable of reading both AC and DC voltage - you'll need this to test the compressor and fan motor circuits. A manifold gauge set designed for automotive or RV refrigeration systems will help you check refrigerant pressures, though this is more for diagnostic purposes since most RV units can't be field-recharged effectively. Note that connecting gauges to refrigerant systems requires EPA Section 609 certification, and any refrigerant handling or recovery must be performed by certified technicians.

For cleaning and maintenance tasks, pick up a good coil cleaner specifically designed for air conditioning systems. Avoid harsh chemicals that might damage the aluminum fins. You'll also want a soft brush for scrubbing, a garden hose for rinsing, and plenty of clean rags. A flashlight or headlamp is essential since you'll be working in tight spaces both on the roof and inside access panels.

Safety equipment is crucial when working on rooftop units. A sturdy ladder rated for your weight plus tools, non-slip shoes, and ideally someone to spot you while you're on the roof. The electrical components in your AC unit can deliver a serious shock, so make sure your multimeter leads are in good condition and you understand basic electrical safety. Always disconnect power at the breaker panel before opening any electrical compartments and use proper lockout/tagout procedures to ensure power cannot be accidentally restored. Warning: Capacitors can hold dangerous electrical charge even when power is disconnected - discharge capacitors safely using an insulated screwdriver across the terminals before handling.

If you suspect refrigerant issues, you'll need a refrigerant leak detector or UV dye kit designed for the correct refrigerant type for your model (verify with dealer). Warning: Adding UV dye to the refrigerant system may void your warranty depending on manufacturer terms and dye type - consult your warranty documentation and dealer before use. However, remember that even if you locate a leak, repairing it and recharging the system typically requires professional equipment and certification. Having the diagnostic tools helps you make informed decisions about whether to attempt repairs or call in a technician.

Doing the Work

Start your diagnosis safely by turning off the AC unit and disconnecting power at your RV's electrical panel. Head up to the roof and remove the shroud covering your Dometic Brisk Air - this typically involves removing several screws around the perimeter. Once exposed, visually inspect the condenser coils for obvious damage, debris, or oil residue that might indicate refrigerant leaks. Look for bent fins, damaged refrigerant lines, or any signs of corrosion.

Clean the condenser coils thoroughly using your coil cleaner and soft brush. Work from top to bottom, being gentle with the aluminum fins as they bend easily. Rinse with low-pressure water, making sure not to force water into electrical components. While the coils dry, check the fan blade for damage and ensure it spins freely. A bent or damaged fan blade can reduce airflow significantly, leading to poor cooling performance.

Next, examine the evaporator coils inside your RV. These are typically accessed through a return air grille in your ceiling. Remove the filter and look at the coils with a flashlight - they should be clean and free of ice buildup. If they're dirty, clean them carefully with coil cleaner, being extra cautious around the fragile fins. If you see ice buildup, this indicates either restricted airflow, low refrigerant, or a failing expansion valve.

Now for the electrical diagnosis. With power restored, use your multimeter to verify that the compressor is receiving proper voltage when the unit is calling for cooling. Listen carefully for compressor engagement - you should hear a distinct click when it starts, followed by a different sound as it runs. The compressor should show continuity between terminals when tested with power off, and should draw significant amperage when running (check manufacturer specs for normal amp draw range). A compressor that draws very low amperage might be running but not actually compressing refrigerant due to internal failure.

Check the capacitors if your unit isn't starting properly or seems to be struggling. The start and run capacitors are typically located in an electrical compartment near the compressor. These cylindrical components can fail over time, preventing the compressor from starting or running efficiently. Test capacitors with a multimeter or capacitor tester to verify they're within manufacturer specifications. A multimeter with capacitance testing capability can verify if they're within specification, or you can swap in known-good capacitors for testing.

If all electrical components test good and the coils are clean, but you're still getting warm air, common causes include refrigerant-related issues. Look more carefully for signs of leaks around all fittings, joints, and coil connections. Oil residue or green discoloration around copper fittings often indicates leak points. UV dye can help locate small leaks if you have the proper UV light for detection.

Time for a Pro

Call in a professional RV technician or HVAC specialist when you've confirmed that refrigerant levels are low or when you've found evidence of refrigerant leaks, when electrical components test faulty, or when the compressor shows signs of internal failure. Professional diagnosis and repair is required for refrigerant system work, as it requires EPA certification and specialized equipment for proper handling and disposal of refrigerants.ce of refrigerant leaks. Unlike automotive AC systems, most RV rooftop units aren't designed for field recharging, and the work requires EPA certification for handling refrigerants. A qualified technician can properly recover any remaining refrigerant, locate and repair leaks, vacuum the system to remove moisture and air, and recharge with the correct amount of refrigerant.

If your testing reveals a failed compressor - indicated by proper voltage but very low amperage draw, or no amperage draw at all despite proper electrical connections - professional replacement is typically the most cost-effective option. Compressor replacement on a rooftop RV unit involves refrigerant recovery, brazing new connections, and system evacuation and recharge. The labor costs often approach the price of a new unit, especially on older systems.

Consider professional help when dealing with electrical issues beyond basic troubleshooting. If you're finding multiple failed components, inconsistent voltage readings, or problems with the control board, an experienced RV technician can diagnose complex electrical faults more efficiently than trial-and-error part replacement. They'll also have access to technical service bulletins and updated wiring diagrams for your specific Dometic model.

The decision point for professional repair versus replacement often comes down to age and overall condition. If your Dometic Brisk Air is more than eight years old and requires major refrigeration system work, replacement might be more economical long-term. Newer units are more energy-efficient and often come with better warranties. A professional can help you evaluate whether investing in repairs makes sense or if you'd be better served by upgrading to a new unit. They can also properly dispose of the old refrigerant and ensure your new installation meets current codes and manufacturer specifications, with all components torqued to manufacturer specifications.