Jeep Transmission Temperature Control Unit
This project was a self-initiated effort to address recurring overheating issues in a 1997 Jeep Cherokee XJ Sport, particularly affecting the automatic transmission during highway driving and summer conditions. While aftermarket transmission coolers are common solutions, this design went further by integrating a custom-built, Arduino-based smart control unit. The system monitored transmission fluid temperatures at three points in the cooling circuit and automatically regulated an auxiliary electric cooling fan using a custom algorithm. A 3D-printed in-cabin interface provided live feedback through an LCD display, offering both automatic and manual fan control.
The project combined mechanical design, heat transfer analysis, electrical engineering, and embedded systems programming to create a robust, field-tested solution. Beyond solving a practical vehicle problem, it demonstrated the ability to integrate multidisciplinary engineering principles into a reliable product that has performed successfully over thousands of miles.
System Design and Circuitry
The system required the design of a complete electronic control circuit capable of interfacing with the Jeep’s 12-volt electrical system while maintaining compatibility with Arduino’s 5-volt logic. This involved researching and implementing relays, voltage regulators, and sensor interfaces to safely manage power delivery. Considerable self-directed learning in electrical and computer engineering was required, including circuit design, breadboarding, and component testing. The final layout ensured that, in the event of system deactivation or failure, the vehicle’s ECU regained full control of the fan, preserving factory safety functionality. This redundancy highlighted the importance of designing fail-safe systems in automotive applications.
Thermal Management & Cooling System Integration
From a mechanical perspective, the project focused on optimizing transmission fluid cooling. Three thermocouples were installed: one at the transmission outlet, one after the factory radiator circuit, and one after the auxiliary cooler. These inputs provided data to evaluate fluid temperature drop across each stage and informed the control logic for fan activation. Selection of a properly sized transmission cooler, evaluation of airflow from the auxiliary fan, and placement of sensors were guided by heat transfer principles and iterative testing. The arrangement ensured that hot fluid was effectively cooled before re-entering the transmission, while also providing the control system with accurate real-time performance feedback.
Embedded Programming & Control Logic
The Arduino microcontroller was programmed in C++ to process temperature inputs, run a custom control algorithm, and trigger fan activation under defined conditions. Unlike a simple threshold-based system, the algorithm considered temperature differentials between multiple sensors to determine when and for how long the fan should operate. This approach reduced unnecessary cycling and optimized cooling efficiency. Manual override functions and display brightness controls were also programmed, demonstrating the flexibility of microcontroller-based systems. Development of this software required a deeper understanding of Arduino memory management, real-time data handling, and input/output coordination between sensors, relays, and displays.
Skills Learned
The TTCU project provided practical experience in cross-disciplinary engineering, blending mechanical, electrical, and software skills. From the electrical side, it reinforced knowledge of circuit design, sensor integration, and power management within a 12-volt automotive environment. From the mechanical perspective, it emphasized thermal management, system redundancy, and the importance of component robustness in high-temperature, vibration-heavy environments. Programming the Arduino microcontroller developed embedded systems skills, including algorithm design, real-time data handling, and hardware-software integration. Equally important were the skills in fabrication and presentation. Designing waterproof housings, implementing cooling solutions for electronics, and creating a custom 3D-printed user interface demonstrated the ability to translate functional requirements into professional, durable hardware. This project highlighted not only the technical problem-solving required to address a real vehicle challenge, but also the adaptability to self-teach outside of coursework and deliver a polished, reliable solution. Collectively, these experiences mirror the type of multidisciplinary problem-solving and systems thinking that are essential in professional engineering practice.