If the fan runs but the air is not cold, the first three things to check are the same in every maker's manual: the power supply and breaker, the thermostat mode and setting, and the return air filters. Coils, wiring and refrigerant are technician work.
RV Air Conditioner Not Cooling: What to Check, in Order
At a glance
- Check in this order: power and breaker, then the thermostat mode and setting, then the filters, which is the order Dometic, Coleman-Mach and Furrion all print.
- How cold is normal: Coleman-Mach says air entering its units leaves about 15 to 20 degrees cooler; Dometic and Furrion publish no equivalent figure.
- Wait before you restart: at least three minutes per Dometic's 2025 manual, two to three minutes per Coleman-Mach, because restarting sooner can trip the breaker.
On this page (8)
Sort the symptom first
The checks depend on whether the unit is dead, blowing warm, icing up or shutting itself down. Find your row, then work through the checks in that order.
| Symptom, in the maker's wording | Owner checks the manual lists, in order |
|---|---|
| The product does not operate (Dometic) | Set or reset the circuit breaker; replace a blown fuse; confirm the generator is running and producing power; confirm the shore cord is plugged in and properly sized for the load |
| Rooftop air conditioner does not switch on (Furrion) | Check the power supply; check the electrical fuse of the power supply. Low voltage goes to an authorized service agent |
| Not cooling well (Furrion) | Set the unit to cooling; select a lower temperature; remove leaves and dirt from the rooftop ventilation grilles. Fan and blower faults go to a service agent |
| Does not maintain the desired temperature (Dometic) | Park in shade; use shades, blinds or curtains; keep windows and doors closed; avoid heat producing appliances; run High Fan or Cooling; start the unit before the outside temperature rises |
| Frost forms on the evaporator coil (Dometic) | Inspect and clean the filter; open the air vents and remove obstructions |
| Constantly switches itself off (Furrion) | Freeze sensor has tripped: outside temperature too low, or all air nozzles closed |
Rows from Dometic's 2025 rooftop air conditioner manual and the Furrion Chill manual.
Power and the thermostat
Start with the breaker, then the fuse, then the supply: on a generator, confirm it is running and producing power; on shore power, confirm the cord is plugged in and sized for the load. Systems with an electronic thermostat have a second fuse to check, the 12-volt one, which the Comfort Control Center 2 instructions list beside the 120-volt one. Low supply voltage is not an owner fix: Furrion sends it to a service agent and Coleman-Mach to a qualified technician.
Then check what the control is asking for. The first two causes of "not cooling" in both Dometic's and Furrion's manuals are a unit not set to cool and a set temperature that is too high. On Dometic's mechanical controls the light gray fan positions are fan only; on Furrion's, the temperature knob works only in COOL mode.
Tip: Air without cold for the first couple of minutes is normal. A Dometic Single Zone LCD thermostat starts the fan first and the compressor about two minutes later, and an Airxcel 9420 digital thermostat holds the compressor for three minutes after a demand is satisfied.
On Dometic controls the error code narrows it down. E7 means 120-volt power to the module boards is lost, which points back to the breaker, cord or generator. E5 means the freeze sensor circuit is open or out of range, and cooling is locked out while the fan runs. Before a service call, note the model and serial numbers on the label visible through the filter opening.
Airflow you can fix yourself
Dirty filters are the one cause the makers expect the owner to clear. Coleman-Mach calls the filters "about the only thing you, the owner, must take care of", and warns that a clogged one cuts the air volume and can ice the coil.
- Open the return air grille (tabs or two quarter-turn fasteners on Coleman-Mach ceiling assemblies; the grille on a Dometic air distribution box).
- Take out the filter or filters. Dometic says never run the unit without both filters in place on its twin-filter boxes.
- Wash in warm soapy water, let the filter dry completely, then refit it.
- On a Furrion, also clear leaves and dirt from the rooftop grilles and the condensation drain openings.
The coils and anything inside the rooftop shroud are not owner work: none of the three makers gives an owner procedure for cleaning them. For the full upkeep routine, see RV air conditioner maintenance.
Tip: The makers disagree on how often. Dometic and Coleman-Mach say at least every two weeks of operation; Furrion says every four weeks in use, with replacement at least every 12 months.
Running but only warm air
First decide whether the unit is really underperforming. Coleman-Mach says its units cool the air about 15 to 20 degrees: 80°F return air should leave the grilles at 60 to 65°F, and while that difference holds the unit is at capacity. Dometic and Furrion print no such figure.
If the difference is there and the RV is still hot, the problem is heat coming in, not the air conditioner. Dometic's remedies are shade, window coverings, closed windows and doors, no heat-producing appliances, High Fan with cooling, and starting the unit before the day warms up. Cycling is normal too: the compressor switches off once the set temperature is reached while the fan keeps running. For how the unit itself works, see RV air conditioners explained.
Freeze-up and shutdowns
Ice on the coil shows up as very cold air at very low speed. The makers name different outside temperatures and different fixes.
| Maker | Outside temperature it names | What the manual tells the owner to do |
|---|---|---|
| Dometic (2021 and 2016 editions) | "Relatively low", no figure printed | Clean the filter, open the vents, turn the thermostat counterclockwise to a warmer setting, run any Fan Only setting until the coil is clear, then contact the service center if it persists |
| Coleman-Mach | Below 75°F in the evening or at night | Set the thermostat midway between Warmer and Cooler; if it ices, run HIGH FAN at maximum air flow until full air flow returns |
| Furrion Chill | 78°F (25.5°C) or below ambient | Do not use MAX COOL at night, keep at least two duct vents open; clear ice by running HIGH FAN for half an hour, and protect the floor from drips |
A unit that keeps switching itself off is, on a Furrion, the freeze sensor tripping because it is too cold outside or every vent is closed. Coleman-Mach units with the factory high-pressure switch lock the compressor out after an abnormal condition, such as dirty filters, and stay locked out until the power is switched off and back on. Repeated lockouts need a technician.
Breaker trips and restart waits
The cause the manuals name is restarting too soon. The compressor cannot start against high pressure, which takes two to three minutes to settle according to Coleman-Mach, and an early restart can trip the breaker. Dometic's 2025 manual says wait at least three minutes.
| Unit | Circuit protection | Minimum wire or cord | Generator, maker's general guideline |
|---|---|---|---|
| Dometic Penguin II, 640312 and 640315 families, 120 VAC 60 Hz (2016 specifications) | 20 A time delay fuse or breaker | 12 AWG copper up to 24 ft | 3.5 kW for one unit, 5.0 kW for two |
| Coleman-Mach 45000 Series, 115 VAC 60 Hz | 20 A time delay fuse or breaker | 12 AWG up to 25 feet, larger beyond | Not published |
| Furrion Chill FACR13HESA2 and FACR15HESA2, 115 V 60 Hz | 20 A | AWG12 power cord | Not published |
| Furrion Chill FACR10HESA2 | 15 A | AWG14 power cord | Not published |
From each maker's manual, including the Dometic Penguin II specifications; Dometic adds that the rest of the RV's load comes on top of its generator figures. Check your own unit's data label rather than another model's figures. If the breaker keeps tripping after a proper wait, Coleman-Mach says to have an electrician check the starting and running amperage.
Where to stop
Every manual puts two things off limits. The 120-volt wiring is work for a qualified service person or electrician in Dometic's, Coleman-Mach's and Furrion's words. The sealed refrigerant system is for a certified technician: Dometic says anyone opening it should hold a current certificate, and Furrion's newer R32 units carry a flammable-refrigerant warning and send any leak or recharge to a service agent. Filters, grilles, drains, the thermostat, the breaker and the restart wait stay yours, much as most water pump faults are, or a water heater that will not light.
Common questions
Why is my RV air conditioner blowing air but not cooling?
The first causes in the makers' tables are the control: the unit set to fan only, or a set temperature that is too high. The fan also keeps running when the compressor cycles off at the set temperature, which is normal. After that, clean the return air filters.
What are common problems with RV AC units?
In the Dometic, Coleman-Mach and Furrion manuals the owner-level ones are a tripped breaker or blown fuse, no power from the generator or shore cord, a control left in fan mode, clogged filters or blocked vents, frost on the coil, and more heat coming in on a hot day than the unit can remove. Fan, blower and refrigerant faults go to a service agent.
Can an RV air conditioner be repaired?
Yes, but the makers split the work. Filters, grilles, drains, thermostat settings and the breaker are owner items; electrical work and anything in the refrigerant circuit are for qualified or certified technicians. None of the three makers publishes part prices.
Why does my RV AC keep tripping the breaker?
The manuals point to restarting too soon: the compressor cannot start against high pressure, which takes two to three minutes to settle. Wait at least three minutes after switching off. If it still trips, Coleman-Mach says to have an electrician check the amperage.