The most common reasons an RV AC runs but doesn't cool: dirty air filter (5-minute fix), failed run capacitor (most common mechanical failure, $20–$40 fix), insufficient power from a 30-amp pedestal, or an ambient temperature above 100°F overwhelming the unit's capacity. Start with the filter — a clogged filter is responsible for at least 40% of AC complaints.
Tell our AI your RV model and AC symptoms — we'll walk you through the diagnosis step by step.
Get Free Diagnosis →The return air filter is located inside your RV on the ceiling shroud directly below the rooftop unit. Pop off the plastic cover and remove the foam or mesh filter. If it's visibly gray or you can't see light through it, wash it with mild soap and water, let it dry fully, and reinstall. A completely blocked filter reduces cooling by 30–50% and can cause the unit to ice up.
RV air conditioners are the biggest power consumers in your RV. A 13,500 BTU unit draws 1,400–1,700 watts running and 3,000–5,000 watts at startup.
The run capacitor is a cylindrical part inside the AC's electrical box (accessible from the roof). It stores and releases energy to help the compressor and fan motor start and run efficiently. When capacitors fail — which happens frequently after 5–8 years — the compressor hums or doesn't start, and the AC either blows warm air or trips a breaker.
Signs of a failed capacitor: AC fan runs but compressor doesn't start, loud hum then the unit trips, or you need to "jump-start" the compressor by hitting the AC on/off rapidly. Measure with a multimeter set to capacitance (μF mode) — the measured value should be within 10% of the rating printed on the side of the capacitor.
The evaporator coil (inside, cold side) and condenser coil (rooftop, hot side) both accumulate dirt that blocks airflow and heat transfer. Accessing the rooftop coil requires removing the outer plastic shroud from the roof. Spray the coils with AC coil cleaner and rinse. This is a good annual maintenance task that noticeably improves cooling on older units.
If your AC is running but produces little air and you see frost or ice on the coils, it's icing up. This happens when the filter is severely clogged, the evaporator coil is dirty, the refrigerant is low, or when outside temperatures are too cool for the AC to operate properly (below 60°F).
Fix: Turn the AC to "fan only" mode for 30–60 minutes to thaw the coils. Then clean the filter and coil before resuming cooling. If it continues to ice up, the refrigerant level may be low — this requires a certified HVAC technician to recharge the system.
If your AC is 10+ years old and failing, replacement is often more economical than repeated repairs. Modern units are significantly more efficient than older ones. The Dometic Brisk II and Coleman Mach 15 are the two most common replacements and require no roof modification if replacing a same-footprint unit.
Still not sure what's wrong with your AC? Our AI can diagnose it — just describe what's happening.
Ask the RV AI →The most common causes are a clogged air filter, a failed run capacitor, low campground voltage (below 104V), or ambient temperatures above 95°F exceeding the unit's capacity. Check the filter first — it's a 5-minute fix that solves 40% of RV AC complaints.
Not without a soft-start kit. A standard 13,500 BTU AC draws 3,000–5,000 watts at startup — far more than a 2,000W generator can provide. With a Micro-Air EasyStart or similar soft-start device, the startup draw drops to 600–900 watts and the AC can run on most 2,000W generators.
A well-maintained RV rooftop AC lasts 10–15 years. The compressor is the most expensive part — if it fails after year 8–10, replacement of the entire unit is often cheaper than compressor repair. Capacitors typically need replacement at years 5–8 for under $40.
Water dripping inside from the ceiling register means the condensate drain pan is overflowing. This happens when the drain holes are clogged with algae or debris. Access the rooftop unit and clear the drain holes in the evaporator pan — use a thin wire or compressed air. Also ensure the RV is level — an unlevel RV causes condensate to pool on one side of the pan and overflow.
RV AI Help provides general information only. Capacitor replacement involves high voltage — always discharge before handling. Product links are affiliate links.