The condenser fan blade sits in the rooftop section of your Dometic Brisk Air unit, mounted directly on the motor shaft above the condenser coil. When the A/C runs, this blade draws outside air down through the shroud and across the hot condenser coil, carrying away the heat that the refrigerant system is transferring out of your RV. Without adequate airflow across the condenser, the refrigerant can't release heat efficiently – the system loses cooling capacity, head pressure rises, and the compressor works harder and runs hotter.AftermarketDirect-FitReplaces 3313107.015
Fan blades fail in predictable ways in RV applications. Plastic fatigue from years of UV exposure and thermal cycling causes the material to become brittle. Road vibration creates micro-fractures at the blade roots. In some cases, a single failed blade breaks off entirely at high RPM – creating a sudden severe imbalance that transmits intense vibration through the motor shaft and bearings, potentially damaging the motor if the unit continues to run. The NBK 20370-2 replaces the failed blade with a fresh polypropylene assembly before that chain of damage progresses.
Exact OEM dimension for full airflow
More blades for efficient heat transfer
Keyed hub fits motor shaft without slipping
OEM-spec performance at lower cost
The NBK 20370-2 uses a 6-blade design molded from polypropylene – the same material type as the original Dometic blade. Six blades provide more air-moving surface area per revolution than a 3- or 4-blade design, resulting in higher airflow volume at the same motor RPM. More airflow across the condenser coil means more efficient heat rejection, which directly translates to better cooling performance inside the RV.
Polypropylene is the material of choice for RV A/C fan blades because it balances stiffness with impact resistance. It holds blade geometry precisely at operating speeds without the aerodynamic distortion that can occur with more flexible materials, while still being able to deflect rather than shatter if it contacts a light debris particle. It also resists the ozone and UV degradation that affects other plastics in rooftop outdoor applications.
The center hub is bored with a D-shaped 1/2" hole that matches the D-profile (flat-cut) shaft on the Brisk Air fan motor. The D-profile is what prevents the blade from rotating independently on the shaft under load – without this feature, a round-bore blade would spin freely on the shaft and move no air at all. The set screw tightens against the flat of the shaft to lock the blade in axial position.
Hub dimensions: The center base measures 4" in diameter and 1-3/8" thick – matching the hub depth of the original blade to ensure the fan blade sits at the same position on the shaft as the OEM part, maintaining proper clearance from the condenser coil and shroud walls.
Screw Side Faces the Motor: This is the most common installation mistake on this blade. The side of the blade with the visible hub set screws must face toward the motor – not away from it. Installing it reversed will position the blades at the wrong pitch relative to airflow direction and significantly reduce cooling performance. Tighten Set Screw to the D-Flat: Before tightening the set screw, rotate the blade on the shaft until you feel the set screw align with the flat section of the D-shaft. Tighten firmly at that point. A set screw bearing on the round portion of the shaft will not hold the blade securely at operating speed. Inspect Motor Shaft Condition: While the blade is off, inspect the motor shaft for corrosion, scoring, or wear at the set screw contact point. A damaged shaft surface can prevent proper blade retention even with correct installation. Check Balance After Installation: Once installed, manually spin the blade by hand before powering up to confirm it rotates freely and evenly with no scraping or wobble. Any wobble indicates the blade is not seated squarely on the shaft.
The NBK 20370-2 is compatible with a broad range of Dometic Duo-Therm Brisk Air A/C and heat pump units. This blade fits the original Brisk Air series – not the Brisk Air II. Always confirm your unit's model number before ordering.
Compatible Brisk Air A/C Series: 532, 546, 548, 557, 558, 559, 570, 578, 579, 589, 590, 595 Compatible Brisk Air Heat Pump Series: 390, 591 Compatible Unit Model Numbers: 57912, 57915, 59136, 59146, 59156, 59516, 59530, B3351
The NBK 20370-2 (Dometic 3313107.015) fits the original Brisk Air series only. If your unit is a Brisk Air II (model numbers beginning with B59xxx or B57xxx such as B59146, B59186, B59196, B59516, B59530, B57915), you need the NBK 20435-1, which replaces Dometic part 3310709.005. Check the data label on your A/C unit's rooftop shroud for the full model number before ordering. The two blades are not interchangeable.
The NBK 20370-2 is a direct replacement for all of the following Dometic/Duo-Therm part numbers: • 3313107.015 (primary OEM part number) • 3313107.0150000001 (extended format of same OEM number) • 3107914.008 (alternate OEM part number) • 317937.000 (earlier OEM part number for same application) If any of these numbers appear on your original blade or in your unit's parts list, the NBK 20370-2 is the correct aftermarket replacement.
Install with set screw side facing the motor. Reversing the blade orientation reduces airflow efficiency significantly. When in doubt, look at the blade pitch – the leading edge of each blade should scoop air downward through the shroud when rotating in the correct direction.
When replacing the condenser fan blade, inspect and consider replacing: Fan Motor (NBK 20370 / Dometic 3313107.041) – If the blade failure was caused by bearing roughness or motor shaft wobble, the motor may need replacement as well. A bad motor will quickly damage a new blade. Run Capacitor – A weak capacitor causes the motor to run below full speed, which strains both the motor and the blade under load. Evaporator Blower Wheel – If the unit hasn't been serviced in several years, inspect the interior blower wheel for debris buildup and blade condition while the rooftop shroud is accessible.
• Disconnect shore power before servicing the rooftop unit – The fan motor operates on 115V AC; always disconnect all power before accessing the condenser section • Brisk Air (original) only – not Brisk Air II – Confirm your unit model number matches the compatibility list; Brisk II units require NBK 20435-1 (Dometic 3310709.005) • Screw side must face the motor – Reversed installation reduces airflow and can cause overheating of the condenser and compressor • Set screw must engage the D-flat – Tightening against the round portion of the shaft will not hold the blade; the blade can escape the shaft at operating speed and cause serious damage • Aftermarket product – This is an NBK aftermarket replacement, not a Dometic OEM part; it is not manufactured by or affiliated with Dometic/Waeco