MotorGuard™ 15

Aviation-Grade Protection for DC Motor Loads in Experimental Aircraft

Made by a pilot for pilots, the MotorGuard™ 15 is a compact, purpose-built protection module for 12–14 VDC motor-driven accessories in RVs, F-1s, and other experimental aircraft. Each unit is manufactured and assembled in Marion, Iowa, functionally tested after your order is placed, and built to survive vibration, heat, and real aviation environments.

Originally created for smoke-system motors, the MotorGuard™ 15 is suitable for any small DC motor on the aircraft — flap motors, trim motors, cooling fans, boost pumps, actuators, and more.

Why It Matters

When a DC motor is switched OFF, its magnetic field collapses and produces a brief voltage spike. If not controlled at the source, that spike travels backward through the electrical bus that powers that motor, affecting any equipment sharing that same bus path.

The MotorGuard™ 15 captures that shutdown spike directly at the motor terminals, preventing it from ever entering the upstream bus.

Internal Protection System

Inside the enclosure is a sealed, dual-path suppression network engineered for inductive DC motor loads. When the motor turns OFF, the network instantly absorbs and redirects the collapse energy locally.

• No spike enters the motor’s electrical bus

• No arcing in panel switches that feed the motor

• No nuisance breaker trips on that circuit

• No noise injection into radios or EFIS sharing the same bus

All components are mounted on a dedicated internal fixture, strain-relieved, and enclosed in a rigid housing. No service is required — installation is simply attaching two ring-terminated leads to the motor posts.

Features

Enclosure

• Printed in durable silver or black 3D thermoplastic

• Extended rectangular body with six weight-reduction hog-outs

• Weight: 1 1/8 oz.

• Size: 56mm (L) x 18mm (H) x 10mm (T)

• Internal fixture secures the protection network

• Integrated strain-relief bobbin with 18 AWG leads

• Impact-resistant, temperature-stable, vibration-ready

• Manufactured, assembled, functionally tested and packaged in the USA

Electrical Protection

• Designed for 12–14 VDC aircraft systems

• Supports motor loads up to 15A running current

Systems Protected (Indirectly)

The module does not connect to these systems — it protects them by preventing the motor’s shutdown spike from entering the bus they share with the motor:

• Panel-mounted switches and rockers on the same feed

• Circuit breakers and fuses on that circuit

• Avionics bus components (EFIS / EMS / GPS / ADS-B) if sharing the same bus

• Radios and intercom audio systems on that bus

• Voltage regulator and alternator field circuits with shared bus paths

• Auxiliary/boost fuel pump motors

• Flap, trim, and actuator motors

• Contactor coils

• Cooling fans

Any device on the same electrical bus benefits when shutdown noise is stopped at the motor instead of being allowed to travel upstream.

Wiring & Installation

• Red lead (shorter): motor positive terminal

• Black lead (longer): motor negative terminal

• 18 AWG leads with insulated ring terminals

• Polarity schematic printed on the enclosure

• Mounts directly at the motor

• Installation schematic included

What the MotorGuard™ 15 Does for Your Aircraft

• Eliminates motor-shutdown voltage spikes at the source

• Prevents arcing and contact erosion in cockpit switches feeding that motor

• Reduces nuisance breaker trips on that circuit

• Prevents shutdown noise from entering the shared bus

• Helps maintain stable avionics operation when motors turn OFF

• Reduces stress on the alternator field and voltage regulator (shared-bus scenarios)

• Provides a clean, enclosed, professional solution

Condition

• Mint, ready to install

• Built and functionally tested after order

• Non-smoker manufacturing facility

Photos may depict example installations. Sale includes the MotorGuard™ 15 module and leads only.