RV AC Not Cooling Properly? Complete Troubleshooting & Repair Guide

Quick Take

Your A/C units are actually working fine - you're experiencing a common RV phenomenon where cooler outdoor temperatures can paradoxically make it harder to maintain indoor temperatures. When it was 95°F outside and your units knocked off 15 degrees to reach 80°F indoors, that was normal performance. Now at 69°F outside, your A/C is struggling because the temperature differential has changed how heat transfer works in your RV. The fact that opening windows and using exhaust fans alone got you to 75°F while outside air was 69°F shows there's significant heat buildup inside your rig from sun exposure and internal heat sources that your A/C units are fighting against.

Common Causes

The primary issue you're facing is solar heat gain through your RV's roof and walls. Even though the outdoor air temperature is only 69°F, direct sunlight can heat your RV's surfaces to 120°F or higher, creating a massive heat load. Your A/C units appeared to work better in the 95°F weather because they were working harder to overcome the large temperature differential, even though they were actually less efficient in the higher outdoor temperatures.

Internal heat sources are also contributing more significantly now. Your refrigerator, water heater, electronics, and even your body heat add up to substantial BTUs that were less noticeable when fighting 95°F heat but become major factors at 69°F. Additionally, while A/C units operate more efficiently at lower outdoor temperatures, they may cycle more frequently when trying to maintain precise temperatures in moderate conditions where the cooling load varies.

Ductwork issues may also be at play. If you have ducted units, leaky or poorly insulated ducts can lose significant cooling capacity. The return air circulation might not be optimal, causing the units to cycle inefficiently when trying to maintain precise temperatures in moderate weather.

Preparation

Before making any repairs, gather your RV's documentation to identify your A/C unit models and BTU ratings. You'll need to check both the rooftop units and any ducting system. Have a digital thermometer or infrared gun ready to take temperature readings at various points - supply vents, return vents, and around the RV interior.

Check your electrical system first. Ensure both A/C units are getting proper voltage - low voltage can cause units to run but not cool effectively. WARNING: Turn off power at the breaker before performing any electrical testing and use proper safety procedures when checking voltage. You'll also want to inspect your roof vents and ensure all exhaust fans are clean and working properly, as proper air circulation is crucial for A/C efficiency.

Examine your RV's insulation situation, particularly around windows and any roof penetrations. Look for obvious air leaks or areas where conditioned air might be escaping. Note the position of your thermostat - if it's in direct sunlight or near a heat source, it may not be reading actual cabin temperature accurately.

Repair Steps

Start with cleaning both A/C units thoroughly. Remove the interior covers and clean or replace the air filters - dirty filters restrict airflow and reduce efficiency dramatically. Clean the evaporator coils with A/C coil cleaner, and check that the condensate drains aren't blocked. On the roof, clean debris from around the units and ensure the condenser coils are free of dirt and leaves.

Install or improve window coverings to block solar heat gain. Reflective window film, thermal curtains, or RV-specific window covers can significantly reduce your cooling load (see manufacturer specifications for expected reductions). Consider adding a roof vent cover or awning fabric to shade your RV if possible - this single step often solves temperature control issues better than any mechanical repair.

Adjust your cooling strategy for moderate weather. Instead of running both units continuously, try running them alternately or zone-cooling different areas of your RV to prevent them from working against each other and improve overall efficiency. Use your exhaust fans strategically - run them to pull hot air out while the A/C brings cool air in, but don't create negative pressure that fights your cooling efforts.

Check and seal any obvious air leaks around windows, doors, and roof penetrations with appropriate RV sealants. If you have ducted A/C, inspect accessible ductwork for leaks and seal with HVAC mastic or metal-backed tape. Check your thermostat calibration and settings first - use a separate thermometer to verify accuracy. Consider relocating your thermostat if it's getting false readings from direct sunlight or heat sources.

When to Get Help

Call an RV technician if you discover refrigerant leaks, indicated by hissing sounds or oily residue around fittings. Ice formation on evaporator coils typically indicates airflow restrictions or thermostat issues that should be addressed first. Low refrigerant requires professional service and can damage your compressor if ignored. Similarly, if either unit's compressor isn't running but the fan operates, this typically indicates electrical issues or compressor failure requiring professional diagnosis.

Seek professional help if your electrical testing reveals voltage issues, as RV electrical systems can be complex and dangerous to repair without proper knowledge. If you find extensive ductwork damage or suspect your units are significantly undersized for your RV, a technician can properly calculate cooling loads and recommend solutions.

Consider professional consultation if these steps don't improve your situation within a week of implementation. An RV A/C specialist can perform refrigerant pressure tests, check for proper airflow rates, and identify issues like failing capacitors or control boards that aren't obvious to DIY troubleshooting.