Air Conditioner Repair and Service, in detail

Rooftop RV air conditioners from Coleman, Dometic and Furrion are sealed systems. There are no service ports, the refrigerant charge is set at the factory, and compressor, condenser, evaporator and capillary are brazed into one assembly. When that sealed system loses charge or the compressor fails, there is no economical repair: opening it means brazing, evacuating and recharging a unit never designed to be serviced, and doing it properly costs more in labour than a complete replacement unit does. Anyone quoting a recharge on a rooftop unit is describing something that will not hold.

What is repairable is everything outside the sealed system: the run capacitor, the start capacitor, the fan motor, the control board, the thermostat, the wiring and the shroud. Those account for the majority of faults that come through the door. AC replacement, hard start and soft start install runs $750 to $4,500 across two to fourteen hours, and a capacitor sits at the very bottom of that band while a full replacement with a new gasket and a ducted adapter sits toward the top.

• Run and start capacitors measured on a capacitance meter
• Fan motor checked for current draw and bearing drag
• Control board and thermostat tested before any unit is condemned
• Sealed circuit left alone, since there are no service ports to work through

A unit whose fan runs while the compressor hums and then cuts out on thermal overload usually has a failed run capacitor, and that is measured with a capacitance meter rather than guessed at from a bulge in the can. A hard start capacitor adds a brief boost to get a tired compressor turning, and it is a legitimate repair on a unit that has become marginal. What it does not do is reduce the current drawn during starting. A soft start device does the opposite, ramping the compressor up across a couple of seconds so inrush current is a fraction of what it was.

On a 30 amp coach that difference is the entire point. One rooftop unit starting on a 30 amp service, with a converter, a microwave and a water heater already drawing, will trip the breaker, and a soft start is the difference between running the air conditioning and not. It also makes a unit startable on a modest inverter or a smaller generator, which is the other reason owners fit them. On a 50 amp coach with two units and headroom to spare, a soft start buys much less, and we will say so before taking the money.

Every rooftop unit sits on a foam gasket compressed between the unit base and the roof around a rectangular opening, and that gasket is the only thing between your ceiling and the weather. It is squeezed by four bolts running through the interior plenum, torqued to a specification that owners and some installers ignore entirely. Over tightened crushes the foam and it loses its spring. Under tightened leaves a path straight through. Either way water shows up at the ceiling months later and gets blamed on a roof seam while the actual cause is sitting right there.

Any time a unit comes off, the gasket is replaced rather than reused. It costs very little and it is not optional here. The roof deck around the opening gets examined too, because a coach that has been leaking there for a season usually has soft decking that needs repair before a new unit goes down. Setting a new air conditioner onto compromised decking is how a job comes back, and it is one of the few times we will decline to proceed until the roof is sorted first.

Coaches kept near the coast in south Orange County show a specific pattern of air conditioner failure. Salt carried in the marine layer settles on the condenser coil, holds moisture against it, and corrodes the aluminium fins away from the copper tube. Cooling capacity falls gradually, the unit runs longer and longer for the same result, and the owner concludes it must be low on refrigerant when the real problem is that a large share of the fin area has simply gone. Fins also foul with dust and pollen after a Santa Ana wind event, and that part is reversible.

Cleaning a coil properly means the shroud off, a cleaner appropriate to aluminium, a low pressure rinse in the correct direction, and fins combed straight where they are bent over. That is about an hour of labour and it restores real capacity on a fouled unit. Corroded fins that have separated from the tube cannot be restored at all, and once enough of them are gone the unit is at the end of its life regardless of how healthy the compressor sounds.

• Shroud removed so the condenser coil can be seen rather than guessed at
• Coil cleaner appropriate to aluminium, then a low pressure rinse in the correct direction
• Bent fins combed straight and separated fins noted as unrecoverable
• Condensate drain paths at the base pan cleared before the shroud goes back on

Two ceiling arrangements exist and they are not interchangeable. A non ducted unit dumps air straight down through the interior assembly with its controls in the same housing. A ducted unit blows into a plenum feeding runs across the roof to registers in each room, with a thermostat on a wall. Swapping one configuration for the other is a ceiling job as well as a roof job, needing a different interior kit and often new ducting. Owners shopping a replacement on price alone frequently buy the wrong configuration and find out on install day.

Ducted systems also fail in ways non ducted ones cannot. A duct run crushed during an interior remodel starves a room, a missing plenum divider lets supply air short circuit straight back into the return, and a coach with two units on a shared plenum can have them working against each other. All of those present as an air conditioner that will not cool the bedroom, and no amount of work on the unit itself will change the outcome.

When a sealed unit is taken out of service, the refrigerant in it is recovered rather than vented, and that recovery happens under the shop EPA registration. The $45 hazmat charge appears on any job where refrigerant, LP or chemical disposal is involved, and it covers handling, documentation and disposal. It is a flat line rather than a percentage, so it does not grow with the size of the job or with the number of units coming off the roof.

Owners occasionally ask whether a unit can go to a scrap yard with its charge still in it and skip the line. The answer is no, and it is not a shop preference. Recovery is a regulatory requirement, the EPA registration is part of what allows this work to be done here at all, and putting a licence at risk over one line item is not a trade anybody should want.

A travel trailer with one non ducted unit on a 30 amp service is the simplest version of this work and it sits near the bottom of the band. A Class A on 50 amp with two ducted units, a shared plenum and a wall thermostat is a longer job, because both units and the ducting have to be balanced once the work is done. A bus conversion is the interesting case: many carry roof units retrofitted by a builder into openings that were cut rather than moulded, and the framing around those openings is whatever the builder decided it should be.

Food trucks and workshop vans bring heat load rather than configuration problems. A galley with a griddle running produces far more heat than an RV unit was ever sized to remove, and fitting a bigger rooftop unit to a vehicle with a limited electrical service does not work. The answer is usually a second unit on its own circuit plus a frank conversation about what the shore connection can actually support, which is a less appealing answer than a bigger box.