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Heater flaps

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DISPLAYING 17 to 21 (of 21 products)
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90121100100B
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Product Information
Heat exchanger heater flaps - Black powder coated. Not for G50 cars
SET OF 2 

Fits:
Porsche 911 Carrera, 3.2, 8/1983 - 7/1986
Porsche Carrera Sport, 3.2, 8/1983 - 7/1986
Porsche 911S (mech. inj.), 2.4, 8/1971 - 7/1973
Porsche 911SC/911 Carrera, 2.7-3.0, 8/1975 - 7/1983
Porsche 911SC/Turbo (930T), 3.3, 8/1978 - 7/1986
Porsche 911T/E/S (not mech. inj.), 2.0-2.4, 1/1963 - 7/1973
Porsche 911/911S/911 Carrera, 2.7, 8/1973 - 7/1975
Porsche 912 Export Model USA
Porsche 912 Model Europe

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Related, superseded, cross reference or alternative numbers for comparison.

90121100100B
90121100700
90121100800
90121100822
90121100722

The product you are viewing cross references to these numbers
90121100100
Product Information
Product Information
Heater Flap Boxes In Stainless Steel (Not For G50 Cars)
SET OF 2
Upgrade the durability and reliability of your classic Porsche's heating system with these OE Match Heater Flap Boxes in Stainless Steel, manufactured as a direct replacement. Designed for models not equipped with the G50 gearbox, these heater flap boxes retain the original fit and function while offering the added corrosion resistance of stainless steel construction.

Fits:
  • Porsche 911 1965-1968 2.0L / 912 SWB (F)
  • Porsche 911 1968-1973 2.2L / 2.4L / 2.7L RS LWB (F)
  • Porsche 911 1974-1977 2.7L / 1976-77 3.0 Carrera
  • Porsche 911 1978-1983 3.0L / SC
  • Porsche 911 1984-1986 3.2L
  • Porsche 911 1987-1989 3.2L G50
  • Porsche 911 1975-1977 3.0L Turbo (930)
  • Porsche 911 1978-1989 3.3L Turbo (930)  

Heater flap boxes regulate the flow of warm air from the heat exchangers into the cabin, providing effective heating and windscreen demisting. Original mild steel units are prone to corrosion from moisture, road debris, and repeated heat cycles, which can cause the flap mechanism to seize or the housing to deteriorate. These stainless steel OE Match replacements provide a long-lasting solution, making them ideal for both regular maintenance and high-quality restoration projects.  

What This Product Does:
  • Control the flow of heated air from the heat exchangers.
  • Direct warm air into the cabin when heating is selected.
  • Divert airflow when cabin heat is not required.
  • Support effective windscreen demisting and defrosting.
  • Restore smooth operation of the heating control system.
  • Provide improved corrosion resistance with stainless steel construction.
  • Replace worn, corroded, or seized original heater flap boxes.

Symptoms Of Wear Or Failure:

  • Poor or inconsistent cabin heating.
  • Reduced airflow through the heating system.
  • Heater remaining on or off regardless of control position.
  • Seized or stiff heater flap mechanism.
  • Corrosion or rust on the flap box housing.
  • Air leaks around the heater flap assembly.
  • Rattling or vibration from underneath the vehicle.
  • Difficulty operating the heater controls.
  • Visible holes or deterioration caused by corrosion.
  • Damaged or missing heater flap boxes.

Why Replacement Matters:
  • Faulty heater flap boxes reduce the efficiency of your Porsche's heating and ventilation system, affecting cabin comfort and limiting the ability to demist or defrost the windscreen. Corroded housings and seized flaps can also allow unwanted air leaks and prevent accurate temperature control.
  • Replacing worn flap boxes restores proper airflow management and dependable heater operation while the stainless steel construction offers significantly greater resistance to corrosion than the original mild steel units. This helps extend service life, reduces future maintenance, and preserves the reliable performance and factory-style operation of the heating system, making these OE Match flap boxes an excellent upgrade for classic Porsche ownership and restoration.



Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

90121100100
90121100700
90121100800
90121100822
90121100722

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Special Order item
91157105101
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Product Information
Heater Control Box Flange.

porsche

Fits:
Porsche 911 1974-89
Porsche 930 TURBO

Click 'Zoom in' for large parts diagram.
Diagram ref no 21

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91157105101
91157105100
91157105101

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91121129700/4
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Product Information
Pair of heater flap blanking plates.

Fits

Porsche 911 1969 to 1989

3D printed in ABS plastic this blanking plate is used when deleting the 911 heater flap boxes

Lightweight and suitable for cars without heating

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Related, superseded, cross reference or alternative numbers for comparison.

91121129700
91121129700

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91121129700/2
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Product Information
Heating block off plate. PAIR.

Fits:
Porsche 911/912 1965-89
Porsche 930 (911) Turbo 1975-89

Replaces number 1 on diagram attached.

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

91121129700
91121129700
91121129704

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DISPLAYING 17 to 21 (of 21 products)
1 2
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About Heater flaps

Porsche Heater Flaps | Precision Airflow Control & Cabin Heating Efficiency

Heater flaps are an essential component in your Porsche’s air distribution and heating system. They control the direction and temperature of air entering the cabin by opening or closing air passages within the ventilation ducts. A properly functioning heater flap ensures balanced temperature control, effective defrosting, and comfortable cabin airflow.

At Design911, we supply high-quality heater flaps and actuators engineered to meet or exceed original performance standards. Each component is designed using durable heat-resistant materials for long-term reliability and smooth operation, ensuring consistent temperature regulation and precise airflow control.

Whether you’re restoring an air-cooled classic or maintaining a modern Porsche climate system, our heater flaps deliver reliable performance, proper sealing, and improved heating efficiency.

What Do Heater Flaps Do?

Heater flaps regulate the distribution and temperature of air in your Porsche’s HVAC system by directing warm or cool air through specific vents.

Core Functions:

  • Control the mix of warm and cool air entering the cabin.
  • Direct airflow to the windscreen, floor, or dash vents as required.
  • Enable quick demisting and defrosting of glass surfaces.
  • Maintain steady interior comfort in all weather conditions.
  • Work in harmony with heater cables or electronic actuators.

Without functional heater flaps, airflow becomes unbalanced — resulting in uneven cabin temperatures, poor ventilation, or ineffective defrosting.

Why Do Heater Flaps Fail or Wear Out?

Heater flaps operate continuously under fluctuating temperatures and airflow pressure. Over time, the mechanisms, seals, or actuators can deteriorate.

Common Causes of Failure Include:

  • Corrosion or rust in metal housings or linkages.
  • Broken flap hinges or worn pivot points.
  • Seized mechanisms from dirt, moisture, or lack of use.
  • Damaged or perished rubber seals causing air leaks.
  • Failed vacuum or servo actuators in electronically controlled systems.

When flaps fail, you may notice inconsistent heating, no airflow from certain vents, or cold air entering the cabin even when the heater is on.

Why Replace Your Porsche Heater Flaps?

Replacing worn or damaged heater flaps restores proper airflow control, prevents heat loss, and improves the overall comfort and efficiency of your heating system.

Key Benefits:

  • Restores balanced airflow and temperature control.
  • Prevents unwanted cold drafts or heat loss.
  • Ensures proper function of demisting and defrosting.
  • Improves cabin comfort in both classic and modern Porsches.
  • Designed for Porsche 911, 912, 914, Cayman, Boxster, Panamera, Macan, and Cayenne models.
  • Perfect for restoration, maintenance, or complete HVAC rebuilds.

Upgrading or replacing old heater flaps also enhances interior air quality and ensures your ventilation system operates as designed.

Highlights

  • Precision-engineered Porsche heater flaps and actuators.
  • Durable, heat-resistant materials for longevity.
  • Direct-fit replacements for Porsche air-cooled and water-cooled models.
  • Essential for consistent airflow and heating performance.
  • Ideal for restoration, maintenance, or upgrade projects.
  • Supports reliable climate control and demisting efficiency.       

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