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7505001 – Hartzell Engine Technologies 12 Volt Positive Brush Assembly
Available now on the Airparts.aero Marketplace.
Overview
The Hartzell Engine Technologies 7505001 is an OEM, factory-new 12-volt positive brush assembly, also known as a brush block or brush card. This is a flight-critical component designed for a wide range of Hartzell and Kelly Aerospace 12-volt aircraft starters commonly found on Lycoming and Continental reciprocating engines. The assembly serves as the primary electrical conductor, securely holding the positive-side carbon brushes and their springs in precise alignment with the starter motor's commutator. Its function is to reliably transmit the high-amperage starting current from the starter's power terminal through the brushes to the rotating armature, which is essential for generating the torque required to crank the engine.
This pre-assembled unit simplifies the overhaul process, ensuring all components are correctly positioned and insulated. It is constructed from a high-temperature, non-conductive phenolic or composite base plate that isolates the positive electrical circuit from the starter's ground (case). The integrity of this assembly is paramount; any failure, such as a cracked plate or a failed brush pigtail, can result in a short circuit or an open circuit, leading to an immediate and complete failure of the starter.
Key Features
OEM Certified Assembly: A genuine Hartzell part, guaranteeing correct materials, precise brush alignment, and reliable performance.
Pre-Assembled Unit: Simplifies maintenance by providing the brushes, springs, and pigtails factory-installed onto the mounting plate, reducing the risk of installation error.
High-Temperature Plate: The brush holder plate is made from a high-dielectric strength, thermally stable composite material to prevent electrical shorts and withstand engine heat.
High-Conductivity Components: Features electrographitic brushes and braided copper pigtails designed for minimal voltage drop under high-current loads.
Optimized Spring Tension: Equipped with pre-installed springs that provide the correct contact force for efficient current transfer and minimal commutator wear.
Technical Specifications
Part Number: 7505001
Component Type: 12V Positive Brush Assembly / Brush Card
OEM Manufacturer: Hartzell Engine Technologies
Voltage Rating: 12 Volts DC
Material (Plate): High-temperature phenolic or glass-phenolic composite.
Material (Brushes): Electrographitic carbon compound.
Material (Pigtails): Tinned braided copper wire.
Governing Specifications: Manufactured as a key component of PMA/TSO-certified starter assemblies.
Aircraft Compatibility
This brush assembly is a core service component for many popular Hartzell/Kelly Aerospace 12-volt starters, including but not limited to:
Starter Models: PM1201, PM1202, PM1203, PM1204, PM1206, PM1207, PE1201, 122-12PM
Engine Applications: A wide range of Lycoming and Continental engines.
These starters are used across a vast spectrum of general aviation aircraft, such as:
Cessna: 172, 182
Piper: PA-28, PA-32, PA-34
Beechcraft: Bonanza, Baron
Mooney: M20 series
Cirrus: SR20, SR22
Note: This is a component part. The starter's specific Illustrated Parts Catalog (IPC) or Component Maintenance Manual (CMM) is the final authority for determining applicability.
Applications
Starter Overhaul: A primary replacement part used by certified repair stations and A&P mechanics during the complete overhaul of Hartzell and Kelly 12V starters.
Electrical System Repair: Used to repair starters that have failed due to worn or damaged positive-side brushes or a compromised brush plate.
Restoration of Starter Performance: Essential for restoring the starter's original cranking torque and electrical efficiency.
Why Choose 7505001?
The 7505001 Positive Brush Assembly is the heart of the starter's electrical circuit. Using a genuine Hartzell assembly ensures that all materials—from the insulation rating of the plate to the conductivity of the brush pigtails—meet the OEM's stringent safety and performance standards. Unapproved or counterfeit assemblies risk using inferior phenolic materials that can crack or carbon-track, leading to a dead short. They may also use improperly sized brushes or weak springs, causing destructive arcing that will quickly destroy the starter's commutator. For reliable engine starting, the certified quality of this OEM assembly is a non-negotiable requirement.
The engineering principle embodied in the 7505001 assembly is the effective isolation and conduction of a high-current DC circuit. As the positive side of the circuit, this assembly must deliver the full potential from the aircraft bus, often exceeding 200-300 amperes, directly to the armature. The brush holder plate acts as a dielectric insulator, with its performance defined by its volume resistivity and dielectric strength, preventing the high current from shorting to the starter's grounded case. The braided copper pigtails are swaged directly to the carbon brushes to create a low-resistance path, ensuring that the majority of the current flows through the pigtail rather than the brush springs, which would cause them to overheat, lose temper, and fail. The entire assembly is designed as an integrated electro-mechanical system to manage the immense current density and thermal stress of a piston engine start cycle.
Note: This is a critical electrical component intended for installation by certified A&P mechanics or authorized repair stations during starter overhaul. All work must be performed in strict accordance with the Component Maintenance Manual (CMM) for the specific starter model. Ensure all electrical connections are clean and torqued to the specified values.
Documentation
No public-facing OEM documentation was located for this specific component part number. All authoritative data, installation procedures, and specifications are contained within the proprietary Hartzell Engine Technologies Component Maintenance or Overhaul Manuals for the parent starter assemblies.
