Duo-Therm RV Furnace Guide: Models, Troubleshooting, Maintenance, and Replacement Parts

Duo-Therm RV furnaces are a common heating choice for recreational vehicles and mobile homes, known for compact design and forced-air performance. This guide explains model differences, common issues, maintenance steps, installation considerations, and where to find replacement parts to keep an RV furnace running efficiently.

Topic	Quick Facts
Common Models	Duo-Therm B, F, and Infinity Series
Fuel Types	Propane (LP) with 12V blower and thermostat control
Typical BTU Range	10,000–35,000 BTU depending on model
Key OEM	Dometic (formerly Duo-Therm brand)

How Duo-Therm RV Furnace Systems Work

Duo-Therm RV furnace units use a propane burner controlled by a thermostat and a 12-volt electrical circuit to power the combustion and blower systems. Air is drawn from the living space, warmed across a heat exchanger, and distributed through ducts. The system relies on a sealed combustion chamber and flue for safe exhaust venting.

Key Components include the gas valve, burner assembly, heat exchanger, combustion blower, distribution blower, thermostat, limit switches, and ignition module or standing pilot depending on model.

Common Duo-Therm Models And Differences

Popular Duo-Therm models include the B-series (compact underbelly or floor-mount units), F-series (higher capacity floor/closet mount), and older Infinity models. Differences center on BTU output, physical footprint, venting style, and blower configuration.

The B-series is suited for small to mid-size RVs with outputs often around 10,000–20,000 BTU. The F-series targets larger rigs and mobile homes with higher BTU outputs and larger blowers. Infinity models may have proprietary control interfaces and require specific replacement parts.

Identifying Your Duo-Therm Furnace Model

Finding the model number is essential before ordering parts or troubleshooting. The data plate is usually located on the furnace’s access panel or blower housing. The plate lists model number, serial number, BTU rating, gas type, and electrical requirements.

If the data plate is missing, measurements of cabinet size, vent locations, and burner configuration, plus photos, can help cross-reference parts with manufacturer catalogs or authorized dealers.

Common Problems And Troubleshooting

Frequent issues include failure to ignite, blower not running, weak airflow, strange odors, and noisy operation. Safety devices like limit switches and thermocouples or flame sensors may cause shutdowns if they detect unsafe conditions.

Failure To Ignite

Check propane supply and tank valve, regulator operation, and an unobstructed LP line. Inspect the gas valve, igniter or pilot assembly, and wiring to the control board. A clogged burner orifice or dirty pilot can prevent ignition.

Blower Runs But No Heat

If the distribution blower runs and air is cold, the burner may not light, or the heat exchanger may be damaged. Verify the thermostat calls for heat, check flame presence, and test the gas valve coil continuity with a multimeter.

Weak Airflow Or No Airflow

Blocked return air, clogged cabin filters, collapsed ducting in underbelly installations, or a failing blower motor can reduce airflow. Inspect ducts, seals, and the blower capacitor and motor for wear or electrical faults.

Excessive Noise Or Vibration

Noisy operation often stems from worn blower bearings, loose mounting screws, or dislodged ducts. Tighten fasteners, lubricate motors where applicable, and replace worn fans. Replace vibration-isolation mounts if deteriorated.

Maintenance Best Practices For Longevity

Routine maintenance enhances safety and reliability. Recommended intervals: inspect visually before each season, perform deeper checks annually, and replace wear items as needed.

• Clean or replace cabin filters and ensure unobstructed return air.
• Vacuum burner and combustion chamber to remove dust and spider webs that can clog orifices.
• Inspect and clean the combustion air intake, flue assembly, and exhaust to prevent carbon monoxide hazards.
• Test thermostat operation and verify wiring integrity.
• Lubricate blower motor bearings only if the motor has oil ports; many modern motors are sealed and require replacement when failing.
• Check for gas leaks using a safe gas leak detector solution—never use an open flame.

Replacement Parts And Where To Buy

Common replacement parts include thermocouples/pilot assemblies, ignition modules, gas valves, limit switches, blower motors, fan blades, control boards, and heat exchanger sections for severe corrosion or damage.

Authorized sources include Dometic parts dealers, RV parts stores, and reputable online retailers. When shopping, confirm the part number and model compatibility. OEM parts preserve fit and safety; aftermarket parts may be less expensive but verify certifications and return policies.

Tips For Ordering Parts

• Always reference the exact model number from the furnace data plate.
• Photograph the existing part and wiring connections for accurate replacement matching.
• Buy replacement gaskets and mounting hardware to ensure proper seals during reinstallation.

Installation And Replacement Considerations

Replacing a Duo-Therm furnace requires adherence to propane and electrical safety codes, plus manufacturer installation instructions. Improper installation risks carbon monoxide leaks, fire hazards, or system failure.

Key installation points: maintain proper clearances, match venting orientation and type, secure the furnace to the subfloor or cabinet, and ensure correct duct runs and return-air paths. Confirm proper flue sealing and clearance to combustibles.

Electrical And Gas Hookup

Furnaces require a 12V DC supply for blower and control circuits and a properly sized propane line with an in-line shutoff. Use marine-grade or RV-rated wiring and connectors, and install overcurrent protection per the furnace manual.

When To Hire A Technician

Hire a certified RV technician or licensed gas fitter for complex replacements, flue repairs, or troubleshooting that involves gas valve replacement and combustion testing. Professional service ensures safe operation and may be required to maintain vehicle insurance or warranty coverage.

Safety Checks And Carbon Monoxide Awareness

Because Duo-Therm furnaces burn propane, regular carbon monoxide (CO) safety checks are essential. Install and test CO detectors in the RV and replace batteries as recommended by the detector manufacturer.

Perform a combustion spillage test and check the flue outlet for soot or discoloration, which can indicate incomplete combustion. If CO or exhaust leakage is suspected, discontinue use until inspected by a professional.

Upgrades And Modernization Options

Owners may upgrade older Duo-Therm units with new thermostats, electronic ignition modules, or higher-efficiency blowers. Replacing outdated mechanical thermostats with programmable or thermostat-controlled DC systems can improve comfort and fuel efficiency.

When upgrading, ensure electrical compatibility and that the furnace control board supports the new thermostat type. In some cases, installing a modern Dometic replacement unit with higher efficiency may be more cost-effective than repeated repairs.

Seasonal Preparation And Winterizing

Before winter, inspect the furnace for debris, test operation, and verify propane system integrity. For winter storage, follow manufacturer guidance: some RV owners keep the furnace accessible to prevent freezing of plumbing areas, while others winterize and disable the system.

During travel in cold climates, monitor furnace operation and cabin temperature. Keep vents and returns clear of snow or ice buildup that could obstruct airflow or flue exhaust.

Resources For Parts, Manuals, And Support

Manufacturer manuals and parts lists are invaluable. Dometic provides online PDFs and parts diagrams for many Duo-Therm legacy models. RV forums, community groups, and technician networks can assist with common repairs and troubleshooting tips.

• Official Dometic Support Pages For Manuals And Parts
• Authorized RV Parts Dealers And Local Service Centers
• RV Owner Forums And Repair Videos For Visual Guidance

Quick Troubleshooting Checklist

Problem	Quick Checks
No Ignition	Verify propane, pilot/igniter, gas valve power, and burned orifice
Blower Not Running	Check 12V fuse, wiring, thermostat output, and blower motor
Weak Heat	Inspect burner, heat exchanger for soot, and airflow restrictions
Unusual Odors	Smell gas, check seals, clean combustion area, test for CO

Final Notes On Maintaining A Safe, Reliable Duo-Therm Furnace

Consistent maintenance and prompt attention to symptoms of trouble will extend the life of a Duo-Therm RV furnace. Use OEM parts where possible, follow installation guidelines, and prioritize safety checks including carbon monoxide monitoring.

For complex issues or anything involving gas valve replacement, heat exchanger cracks, or persistent CO presence, consult a certified RV technician. Proper care keeps the RV warm and the travel experience safe and comfortable.